diff --git a/naive-nlu/tree_nlu/atoms.py b/naive-nlu/tree_nlu/atoms.py
new file mode 100644
index 0000000..d1de20a
--- /dev/null
+++ b/naive-nlu/tree_nlu/atoms.py
@@ -0,0 +1,23 @@
+'''
+Analogous to erlang ones.
+
+"An atom is a literal, a constant with name."
+'''
+
+from collections import namedtuple
+
+Atom = namedtuple('Atom', field_names='name')
+
+def is_atom(element, name=None):
+    '''Check if an element is an atom with a specific name.'''
+    if not isinstance(element, Atom):
+        return False
+
+    if name is None:
+        return True
+
+    return element.name == name
+
+def a(name):
+    '''Build an atom with a given name.'''
+    return Atom(name)
diff --git a/naive-nlu/tree_nlu/knowledge_base.py b/naive-nlu/tree_nlu/knowledge_base.py
index 931801f..389a70a 100644
--- a/naive-nlu/tree_nlu/knowledge_base.py
+++ b/naive-nlu/tree_nlu/knowledge_base.py
@@ -3,22 +3,74 @@ import logging
 
 from .session.org_mode import global_session as session
 
+from .atoms import Atom
 from . import parsing
+from . import tokenization
 from . import knowledge_evaluation
 from .modifiable_property import is_modifiable_property
-
+import random
 
 def diff_knowledge(before, after):
     import jsondiff
     return jsondiff.diff(before, after)
 
 
+def randomized_weighted_list(elements):
+    # Randomized
+    randomized = list(elements)
+    random.shuffle(randomized)
+
+    # And return only once
+    already_returned = set()
+    for e in randomized:
+        if e in already_returned:
+            continue
+
+        yield e
+        already_returned.add(e)
+
+
+
 class KnowledgeBase(object):
-    def __init__(self, knowledge, examples=[], trained=[]):
+    def __init__(self, knowledge={}, examples=[], trained=[]):
         self.knowledge = copy.copy(knowledge)
         self.originals = []
         self.examples = copy.copy(examples)
         self.trained = copy.copy(trained)
+        self.structural_elements = set()
+        self.token_chains = {}
+        self.tokens = set()
+
+    def add_token_pair(self, precedent, consequent):
+        self.add_token(precedent)
+        self.add_token(consequent)
+
+        if precedent not in self.token_chains:
+            self.token_chains[precedent] = []
+        self.token_chains[precedent].append(consequent)
+
+    def add_token(self, token):
+        self.tokens.add(token)
+        if (not isinstance(token, Atom)) and (token not in self.structural_elements):
+            session().annotate('Found new structural element “{}”'.format(token))
+            self.structural_elements.add(token)
+
+    def expected_token_after_precedent(self, precedent=None):
+        if precedent not in self.token_chains:  # If there's no known precedent, just return all tokens
+            return randomized_weighted_list(self.tokens)
+
+        return randomized_weighted_list(self.token_chains[precedent])
+
+    def train_tokenizer(self, example):
+        with session().log('Training tokenizer'):
+            session().annotate("Example: {}".format(example))
+            tokens = tokenization.integrate_tokenization(self, example)
+
+            # Integrate knowledge of concept
+            for token in tokens:
+                if not token in self.knowledge:
+                    self.knowledge[token] = {}
+
 
     def train(self, examples):
         knowledge_before = copy.deepcopy(self.knowledge)
@@ -26,7 +78,7 @@ class KnowledgeBase(object):
             # Parse everything
             for example in examples:
                 # If there's parsed data, leverage it ASAP
-                if 'parsed' in example:
+                if 'parsed' in example and isinstance(example['parsed'], tuple):
                     with session().log('parsed information integration'):
                         result = knowledge_evaluation.integrate_information(self.knowledge, {
                             "parsed": example['parsed'],
@@ -35,7 +87,8 @@ class KnowledgeBase(object):
 
                 with session().log("language integration"):
                     tokens, decomposition, inferred_tree = parsing.integrate_language(self, example)
-                    session().annotate(tokens)
+                    session().annotate("Tokens: {}".format(tokens))
+                    session().annotate("Inferred tree: {}".format(inferred_tree))
 
                 with session().log("full information integration"):
                     result = knowledge_evaluation.integrate_information(self.knowledge, {
@@ -60,11 +113,24 @@ class KnowledgeBase(object):
 
             return knowledge_diff_getter
 
-    def process(self, row):
+    def tokenize(self, row, return_one=True):
         row = row.lower()
+        with session().log("Tokenize: {}".format(row)):
+            options = list(tokenization.to_tokens(self, row))
+            session().log("Results:\n{}".format('\n'.join(map(str, options))))
+
+            if return_one:
+                chosen = tokenization.pick_one_tokenization(options, self)
+                session().log("Chosen: “{}”".format(chosen))
+                self.train_tokenizer({'text': row, 'tokens': chosen})
+                return chosen
+            return options
+
+    def process(self, row):
         knowledge_before = copy.deepcopy(self.knowledge)
         with session().log("Process: {}".format(row)):
-            tokens = parsing.to_tokens(row)
+            tokens = self.tokenize(row)
+
             fit = parsing.get_fit(self, tokens)
             if fit is None:
                 return None
diff --git a/naive-nlu/tree_nlu/parsing.py b/naive-nlu/tree_nlu/parsing.py
index 8081265..f22a4ce 100644
--- a/naive-nlu/tree_nlu/parsing.py
+++ b/naive-nlu/tree_nlu/parsing.py
@@ -1,6 +1,7 @@
 #!/usr/bin/env python
 
 from . import knowledge_evaluation
+from . import tokenization
 
 from . import depth_meter
 from .session.org_mode import global_session as session
@@ -11,11 +12,7 @@ from functools import reduce
 from typing import List, Dict
 from .modifiable_property import ModifiableProperty
 from . import parameters
-
-# TODO: more flexible tokenization
-def to_tokens(text):
-    return re.findall(r'(\w+|[^\s])', text)
-
+from .atoms import Atom, a, is_atom
 
 def make_template(knowledge_base, tokens, parsed):
     matcher = list(tokens)
@@ -87,7 +84,7 @@ def integrate_language(knowledge_base, example):
     parsed = example["parsed"]
 
     resolved_parsed = copy.deepcopy(parsed)
-    tokens = to_tokens(text)
+    tokens = list(tokenization.pick_one_tokenization(tokenization.to_tokens(knowledge_base, text), knowledge_base))
 
     while True:
         session().annotate("P: {}".format(resolved_parsed))
@@ -226,24 +223,35 @@ def all_indexes(collection, element):
 def all_matching_indexes(knowledge_base, collection, element):
     indexes = []
 
-    assert("groups" in element)
-    element = element["groups"]
-    for i, instance in enumerate(collection):
-        if isinstance(instance, dict):
-            instance = instance["groups"]
-        elif instance in knowledge_base.knowledge:
-            instance = knowledge_base.knowledge[instance]["groups"]
+    with session().log('Matching “{}”'.format(element)):
+        assert("groups" in element)
+        element = element["groups"]
+        for i, instance in enumerate(collection):
+            session().log('Checking “{}”'.format(instance))
 
-        intersection = set(instance) & set(element)
-        if (len(intersection) > 0 or (0 == len(instance) == len(element))):
-            indexes.append((i, intersection))
+            if isinstance(instance, dict):
+                instance = instance["groups"]
+            elif instance in knowledge_base.knowledge:
+                session().log('Knowledge about “{}”: ”{}”'.format(instance, knowledge_base.knowledge[instance]))
 
-    return [x[0] for x in sorted(indexes, key=lambda x: len(x[1]), reverse=True)]
+                if "groups" not in knowledge_base.knowledge[instance]:
+                    # This means that is only known as token
+                    # so we should try to avoid using it
+                    continue
+
+                instance = knowledge_base.knowledge[instance]["groups"]
+
+            intersection = set(instance) & set(element)
+            if (len(intersection) > 0 or (0 == len(instance) == len(element))):
+                indexes.append((i, intersection))
+
+        return [x[0] for x in sorted(indexes, key=lambda x: len(x[1]), reverse=True)]
 
 
 def element_matches_groups(knowledge, element: Dict, groups):
+  with session().log("Checking if e “{}” matches groups “{}”".format(element, groups)):
     if isinstance(groups, str) and groups in knowledge:
-        return len(knowledge[element].get("groups", set()) & element['groups']) > 0
+        return len(knowledge[groups].get("groups", set()) & element['groups']) > 0
     elif isinstance(groups, dict):
         return len(element.get("groups", set()) & element['groups']) > 0
     return False
diff --git a/naive-nlu/tree_nlu/test.py b/naive-nlu/tree_nlu/test.py
index 1cdfe11..683f85e 100644
--- a/naive-nlu/tree_nlu/test.py
+++ b/naive-nlu/tree_nlu/test.py
@@ -1,7 +1,8 @@
 import traceback
 import logging
-import datetime
 from .session import org_mode
+
+from .tests import tokenization
 from .tests import basic
 from .tests import gac_100
 from .tests import gac_extension
@@ -9,6 +10,7 @@ from .tests import gac_extension
 logging.getLogger().setLevel(logging.ERROR)
 
 tests = (
+    ("tokenization", tokenization),
     ("basic", basic),
     ("gac 100", gac_100),
     ("gac+", gac_extension),
@@ -24,12 +26,14 @@ def main():
     failed = False
     for test_name, test_module in tests:
         try:
-            test_module.main()
+            with org_mode.global_session().log(test_name):
+                test_module.main()
             print(" \x1b[1;32m✓\x1b[0m {}".format(test_name))
         except AssertionError as ae:
             print(" \x1b[1;31m✗\x1b[0m {}{}".format(test_name,
                                                   ('\n [Assertion] {}'.format(ae.args[0])) if len(ae.args) > 0
                                                    else ''))
+            traceback.print_exc()
             failed = True
 
         except Exception as e:
diff --git a/naive-nlu/tree_nlu/tests/basic.py b/naive-nlu/tree_nlu/tests/basic.py
index 4038bc6..bda8261 100644
--- a/naive-nlu/tree_nlu/tests/basic.py
+++ b/naive-nlu/tree_nlu/tests/basic.py
@@ -3,6 +3,7 @@ import json
 
 from ..knowledge_base import KnowledgeBase
 from ..modifiable_property import is_modifiable_property
+from ..utils.tokenization import train_basic_tokenization
 
 examples = [
     {
@@ -107,6 +108,9 @@ base_knowledge = {
     'swim': {
         "groups": {'verb'},
     },
+    'planet': {
+        'groups': {'noun'}
+    }
 }
 
 def test_assumption(expectedResponse, knowledge, query):
@@ -125,6 +129,8 @@ def main():
         knowledge=base_knowledge,
     )
 
+    train_basic_tokenization(knowledge)
+
     for example in examples:
         with session().log(example['text']):
             differences = knowledge.train([example])
diff --git a/naive-nlu/tree_nlu/tests/gac_100.py b/naive-nlu/tree_nlu/tests/gac_100.py
index 5c57766..f4656fb 100644
--- a/naive-nlu/tree_nlu/tests/gac_100.py
+++ b/naive-nlu/tree_nlu/tests/gac_100.py
@@ -2,6 +2,7 @@ from ..session.org_mode import global_session as session
 from ..knowledge_base import KnowledgeBase
 from ..utils.visuals import show_progbar
 from ..visualization import show_knowledge
+from ..utils.tokenization import train_basic_tokenization
 
 def _assert(args):
     assert(args)
@@ -667,6 +668,10 @@ base_knowledge = {
     'electricity': {
         "groups": {'power'},
     },
+    'airplanes': {},
+    'white': {
+        'groups': {'property'},
+    }
 }
 
 def main():
@@ -674,6 +679,8 @@ def main():
         knowledge=base_knowledge,
     )
 
+    train_basic_tokenization(knowledge)
+
     total = len(examples)
 
     for i, (example_type, data) in enumerate(examples):
diff --git a/naive-nlu/tree_nlu/tests/gac_extension.py b/naive-nlu/tree_nlu/tests/gac_extension.py
index 5aae0a2..abb87ba 100644
--- a/naive-nlu/tree_nlu/tests/gac_extension.py
+++ b/naive-nlu/tree_nlu/tests/gac_extension.py
@@ -22,4 +22,5 @@ def ask_then_learn_test(knowledge: KnowledgeBase):
 def main():
     knowledge = gac_100.main()
 
+    knowledge.knowledge['blue'] = {'groups': {'property'}}
     knowledge = ask_then_learn_test(knowledge)
diff --git a/naive-nlu/tree_nlu/tests/tokenization.py b/naive-nlu/tree_nlu/tests/tokenization.py
new file mode 100644
index 0000000..6b61fc4
--- /dev/null
+++ b/naive-nlu/tree_nlu/tests/tokenization.py
@@ -0,0 +1,80 @@
+from ..session.org_mode import global_session as session
+from ..knowledge_base import KnowledgeBase
+from ..utils.visuals import show_progbar
+from ..visualization import show_knowledge
+
+
+def _assert(args):
+    assert(args)
+
+
+def _assert_msg(args, msg):
+    assert args, msg
+
+
+EXAMPLES = [
+    ('example', {
+        "text": 'cat',
+        "tokens": ['cat'],
+    }),
+    ('example', {
+        "text": 'cats',
+        "tokens": ['cats'],
+        "meaning": { 'cats': ('add-modifier', 'cat', 'plural') },
+    }),
+    ('example', {
+        "text": 'text separated by spaces',
+        "tokens": ['text', 'separated', 'by', 'spaces'],
+    }),
+    ('example', {
+        "text": 'is earth a planet?',
+        "tokens": ['is', 'earth', 'a', 'planet', '?'],
+    }),
+    ('test', {
+        "text": 'plane',
+        "tokens": ['plane'],
+    }),
+    # ('test', {
+    #     "text": 'planes',
+    #     "tokens": ['planes'],
+    #     "meaning": { 'planes': ('add-modifier', 'plane', 'plural') },
+    # }),
+    ('test', {
+        "text": 'some other text',
+        "tokens": ['some', 'other', 'text'],
+    }),
+    ('test', {
+        "text": 'is the sun a star?',
+        "tokens": ['is', 'the', 'sun', 'a', 'star', '?'],
+    }),
+    ('test', {
+        "text": 'sometextnotseparatedbyspaces',
+        "tokens": ['some', 'text', 'not', 'separated', 'by', 'spaces'],
+    })
+]
+
+
+def main():
+    knowledge = KnowledgeBase()
+
+    total = len(EXAMPLES)
+
+    for i, (case_type, example) in enumerate(EXAMPLES):
+        show_progbar(i, total, example['text'])
+        if case_type == 'example':
+            with session().log(example['text']):
+                knowledge.train_tokenizer(example)
+
+        elif case_type == 'test':
+            with session().log(example['text']):
+                tokens = list(knowledge.tokenize(example['text']))
+
+                session().log('Expected “{}”, found “{}”'
+                            .format(example['tokens'], tokens))
+                assert example['tokens'] == tokens
+
+        else:
+            raise Exception('Not implemented case {}'.format(case_type))
+
+    print("\r\x1b[K", end='')
+    return knowledge
diff --git a/naive-nlu/tree_nlu/tokenization.py b/naive-nlu/tree_nlu/tokenization.py
new file mode 100644
index 0000000..7322cb5
--- /dev/null
+++ b/naive-nlu/tree_nlu/tokenization.py
@@ -0,0 +1,186 @@
+from .session.org_mode import global_session as session
+from .atoms import Atom, a, is_atom
+
+def lookahead_for_tokens_or_strucutral_elements(knowledge_base, remaining):
+    for se in knowledge_base.structural_elements:
+        found_position = remaining.find(se)
+        found = found_position >= 0
+        session().annotate('Looking for structure with “{}”, found? {}'.format(se, found))
+        if found:
+            return [
+                (remaining[:found_position], se, remaining[found_position + len(se):])
+            ]
+
+    for token in knowledge_base.knowledge.keys():
+        found_position = remaining.find(token)
+        found = found_position >= 0
+        session().annotate('Looking for token “{}”, found? {}'.format(token, found))
+        if found:
+            return [
+                (remaining[:found_position], token, remaining[found_position + len(token):])
+            ]
+
+    return None
+
+
+
+def to_tokens(knowledge_base, text, precedent=None):
+    if len(text) == 0:
+        session().annotate("No text remaining")
+        yield ['']
+        return
+
+    with session().log("Tokenizing {}".format(text)):
+        for option in knowledge_base.expected_token_after_precedent(precedent):
+            with session().log("Next: “{}”".format(option)):
+                with session().log("Matching “{}” on “{}”".format(option, text)):
+                    for token_match in tokenization_match(option, text, knowledge_base):
+                        if token_match is None:
+                            session().annotate("No match")
+
+                        match, remaining = token_match
+                        if len(remaining) == len(text):
+                            raise Exception('No text consumed in match')
+
+                        session().annotate('Match: “{}”'.format(match))
+                        with session().log('Remaining “{}”'.format(remaining)):
+                            for sublevel in to_tokens(knowledge_base, remaining, match):
+                                candidate = list(filter(lambda x: x != '', [match] + sublevel))
+                                session().annotate('Yielding candidate “{}”'.format(candidate))
+                                yield candidate
+
+
+def tokenization_match(element, text, knowledge_base):
+    # Constant/structural string matching
+    if isinstance(element, str):
+        if text.find(element) == 0:
+            # This match comes from a structuring element
+            # It doesn't appear on the tokenization
+            # So we should return it as an empty string
+            yield ('', text[len(element):])
+            return
+        else:
+            # No match found
+            return
+
+    elif is_atom(element, 'token'):
+        yield from match_single_token(text, knowledge_base)
+        return
+    raise NotImplementedError()
+
+
+def match_single_token(text, knowledge_base):
+    found_token = False
+    for token in knowledge_base.knowledge.keys():
+        if text.find(token) == 0:
+            yield token, text[len(token):]
+            found_token = True
+
+    if found_token:
+        return
+
+    session().annotate('No token found at the start of ”{}”'.format(text))
+    session().annotate('using structural elements to infer it')
+    # TODO: review this when multiple structural elements are available
+    for se in knowledge_base.structural_elements:
+        session().annotate('Looking for se “{}” in “{}”'.format(se, text))
+        position = text.find(se, 0)
+        found = position > 0  # 0 is not considered a valid position for this kind of split
+        if found:
+            session().annotate('Found ”{}”, inferring “{}”'.format(se, text[:position]))
+            yield text[:position], text[position:]
+
+    session().annotate('No structural element or token found, inferring only token remaining')
+    yield text, ''
+
+    # Using other tokens for cutoff
+    for token in knowledge_base.knowledge.keys():
+        session().annotate('Looking for token “{}” in “{}”'.format(token, text))
+        position = text.find(token)
+        found = position >= 0
+        if found:
+            session().annotate('Found ”{}”, in position ”{}”'.format(token, position))
+            yield text[:position], text[position:]
+
+
+def integrate_tokenization(knowledge_base, example):
+    text = example['text']
+    tokens = example['tokens']
+    meaning = example.get('meaning')
+
+    return integrate_token_to_text_matching(knowledge_base, text, tokens)
+
+
+def integrate_token_to_text_matching(knowledge_base, text, tokens):
+    texts = [text]
+
+    # Convert to tokens
+    for token_id, token in enumerate(tokens):
+        # Look for token in texts
+        for i, text in enumerate(texts):
+            if isinstance(text, int):
+                continue
+
+            if token in text:
+                before, after = text.split(token, maxsplit=1)
+                texts = (texts[:i] + [before]
+                         + [a('token')]
+                         + [after] + texts[i + 1:])
+                break
+        else:
+            raise Exception('Token not found')
+
+    # Remove leftovers from splits
+    texts = list(filter(lambda x: x != '', texts))
+    session().log("Tokenized as {} over {}".format(texts, tokens))
+
+    for i, element in enumerate(texts[:-1]):
+       learn_token_pair(element, texts[i + 1], knowledge_base)
+
+    return tokens
+
+def learn_token_pair(precedent, consequent, knowledge_base):
+    knowledge_base.add_token_pair(precedent, consequent)
+
+
+def pick_one_tokenization(options, knowledge_base):
+    '''
+    Heuristic function to pick the most probable tokenization.
+
+    Just pick the one with more results.
+    '''
+    options = list(options)
+    with session().log("Picking among: {} options".format(len(options))):
+        session().log("Options: \n{}".format('\n'.join(map(str, options))))
+        return pick_by_score(options,
+                             [
+                                 # By number of splits without structuring elements
+                                 lambda tokenization: sum(map(
+                                     lambda split: sum(map(
+                                         lambda se: se in split, knowledge_base.structural_elements
+                                     )), tokenization)),
+
+                                 # By number of unknown tokens
+                                 lambda tokenization: len(list(filter(lambda token:
+                                                                      (token not in knowledge_base.knowledge.keys()) and
+                                                                      (token not in knowledge_base.structural_elements),
+                                                                      tokenization))),
+
+                                 # By number of splits
+                                 lambda tokenization: -len(tokenization),
+                             ])
+
+def pick_by_score(options, heuristics):
+    for heuristic in heuristics:
+        assert(len(options) > 0)
+        options = list(map(lambda opt: (heuristic(opt), opt), options))
+        sorted_options = sorted(options, key=lambda x: x[0], reverse=False)
+
+        heuristic_cutoff = sorted_options[0][0]
+        session().annotate(sorted_options)
+        pass_heuristic = [opt for (score, opt) in sorted_options if score <= heuristic_cutoff]
+        options = pass_heuristic
+
+    session().log("{} finalists: \n{}".format(len(options), '\n'.join(map(str, options))))
+    return options[0]
+
diff --git a/naive-nlu/tree_nlu/utils/tokenization.py b/naive-nlu/tree_nlu/utils/tokenization.py
new file mode 100644
index 0000000..4664923
--- /dev/null
+++ b/naive-nlu/tree_nlu/utils/tokenization.py
@@ -0,0 +1,29 @@
+from ..session.org_mode import (
+    global_session as session,
+)
+
+BASIC_TOKENIZATION_EXAMPLES = (
+    ({
+        "text": 'cat',
+        "tokens": ['cat'],
+    }),
+    ({
+        "text": 'cats',
+        "tokens": ['cats'],
+        "meaning": { 'cats': ('add-modifier', 'cat', 'plural') },
+    }),
+    ({
+        "text": 'text separated by spaces',
+        "tokens": ['text', 'separated', 'by', 'spaces'],
+    }),
+    ({
+        "text": 'is earth a planet?',
+        "tokens": ['is', 'earth', 'a', 'planet', '?'],
+    }),
+)
+
+
+def train_basic_tokenization(knowledge_base):
+    with session().log('Training basic tokenization'):
+        for example in BASIC_TOKENIZATION_EXAMPLES:
+            knowledge_base.train_tokenizer(example)