diff --git a/requirements.txt b/requirements.txt
index 7df1ca3..5e24cc7 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -3,14 +3,18 @@
 #
 # Then you probably want to work in a virtualenv (optional):
 #     $ sudo pip install --upgrade virtualenv
-# Or if you prefer you can install virtualenv using your favorite packaging system. E.g., in Ubuntu:
+# Or if you prefer you can install virtualenv using your favorite packaging
+# system. E.g., in Ubuntu:
 #     $ sudo apt-get update && sudo apt-get install virtualenv
 # Then:
 #     $ cd $my_work_dir
 #     $ virtualenv my_env
 #     $ . my_env/bin/activate
 #
-# Next, optionally uncomment the OpenAI gym lines (see below). If you do, make sure to install the dependencies first.
+# Next, optionally uncomment the OpenAI gym lines (see below).
+# If you do, make sure to install the dependencies first.
+# If you are interested in xgboost for high performance Gradient Boosting, you
+# should uncomment the xgboost line (used in the ensemble learning notebook).
 #
 # Then install these requirements:
 #     $ pip install --upgrade -r requirements.txt
@@ -19,26 +23,65 @@
 #     $ jupyter notebook
 #
 
+
+##### Core scientific packages
 jupyter==1.0.0
-matplotlib==2.0.2
-numexpr==2.6.3
-numpy==1.13.1
-pandas==0.20.3
-Pillow==4.2.1
-protobuf==3.4.0
-psutil==5.3.1
-scikit-learn==0.19.0
-scipy==0.19.1
-sympy==1.1.1
-tensorflow==1.3.0
+matplotlib==2.2.2
+numpy==1.14.3
+pandas==0.22.0
+scipy==1.1.0
+
+
+##### Machine Learning packages
+scikit-learn==0.19.1
+
+# Optional: the XGBoost library is only used in the ensemble learning chapter.
+#xgboost==0.71
+
+
+##### Deep Learning packages
+
+# Replace tensorflow with tensorflow-gpu if you want GPU support. If so,
+# you need a GPU card with CUDA Compute Capability 3.0 or higher support, and
+# you must install CUDA, cuDNN and more: see tensorflow.org for the detailed
+# installation instructions.
+tensorflow==1.8.0
+#tensorflow-gpu==1.8.0
+
+# Forcing bleach to 1.5 to avoid version incompatibility when installing
+# TensorBoard.
+bleach==1.5.0
+
+Keras==2.1.6
+
 
 # Optional: OpenAI gym is only needed for the Reinforcement Learning chapter.
 # There are a few dependencies you need to install first, check out:
 # https://github.com/openai/gym#installing-everything
-#gym[all]==0.9.3
+#gym[all]==0.10.5
 # If you only want to install the Atari dependency, uncomment this line instead:
-#gym[atari]==0.9.3
+#gym[atari]==0.10.5
+
+
+##### Image manipulation
+imageio==2.3.0
+Pillow==5.1.0
+scikit-image==0.13.1
+
+
+##### Extra packages (optional)
+
+# Nice utility to diff Jupyter Notebooks.
+nbdime==0.4.1
+
+# May be useful with Pandas for complex "where" clauses (e.g., Pandas
+# tutorial).
+numexpr==2.6.5
+
+# These libraries can be useful in the classification chapter, exercise 4.
+nltk==3.3
+urlextract==0.8.3
 
 # Optional: these are useful Jupyter extensions, in particular to display
 # the table of contents.
-https://github.com/ipython-contrib/jupyter_contrib_nbextensions/tarball/master
+jupyter-contrib-nbextensions==0.5.0