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diff --git a/README.md b/README.md
index 0afb0b724..9e4be1c40 100644
--- a/README.md
+++ b/README.md
@@ -9,24 +9,39 @@ This data can e.g. be used for static analysis, type checking or type inference.
 
 ## Format
 
-Each Python module is represented by a `.py` "stub". This is a normal Python
+Each Python module is represented by a `.pyi` "stub". This is a normal Python
 file (i.e., it can be interpreted by Python 3), except all the methods are empty.
 Python function annotations ([PEP 3107](https://www.python.org/dev/peps/pep-3107/))
 are used to describe the types the function has.
 See [PEP 484](http://www.python.org/dev/peps/pep-0484/) for the exact syntax
 of the stub files.
 
+## Directory structure
+
+We store stubs for both Python 2 as well as Python 3. We also distinguish
+between minor versions (E.g. 3.2 <-> 3.3). To accomplish not having to duplicate
+modules that are the same between all minor versions, we have e.g. a top-level
+directory 3/ that contains all the stubs for Python 3. More specialized stubs
+go into e.g. 3.3/ and supersede the more generic stubs in 3/. (And, if needed,
+a directory 3.3.1/ would be able to supersede stubs in 3.3/):
+
+Directory     |
+------------- | -------------
+2.7/          | Stubs for Python 2.7
+3/            | Stubs for Python 3
+3.3/          | Some specialized stubs for Python 3.3 (replacing generic stubs in 3/)
+
 ## Example
 
 The below is an excerpt from the types for the `datetime` module.
 
 ```
-MAXYEAR = Undefined(int)
-MINYEAR = Undefined(int)
-__doc__ = Undefined(str)
-__file__ = Undefined(str)
-__name__ = Undefined(str)
-__package__ = Undefined(None)
+MAXYEAR = ...  # type: int
+MINYEAR = ...  # type: int
+__doc__ = ...  # type: str
+__file__ = ...  # type: str
+__name__ = ...  # type: str
+__package__ = ...  # type: None
 
 class date(object):
     def __init__(self, year: int, month: int, day: int): ...
@@ -43,9 +58,5 @@ class date(object):
 ## Contributions
 
 We're welcoming contributions (pull requests) for types of third party
-packages. They'll go under python{2,3}/dist-packages/.
-
-## Roadmap
-
-This project will move to https://github.com/python/typeshed/ eventually.
+packages. They'll go under {2.7,3}/dist-packages/.