Python and OpenGL have a long but complicated story. It used to be really easy to program something using the fixed-pipeline and libraries such as Pyglet but things became more difficult with the introduction of the dynamic graphic pipeline in 2004. The goal of this book is to reconciliate Python programmers with OpenGL, providing both an introduction to modern OpenGL and a set of basic and advanced techniques in order to achieve both fast, scalable & beautiful scientific visualizations. The book uses the GLES 2.0 API which is the most simple API for accessing the programmable graphic pipeline. It does not cover up-to-date OpenGL techniques but it is sufficient to achieve great visualisation. In fact, modern OpenGL allows to control pretty much everything in the pipeline and the goal of this book is to explain several techniques dedicated to scientific visualisation such as isolines, markers, colormaps, arbitrary transformations but there are actually many more techniques to be discovered and explained in this open-access book. And of course, everything will be fast and beautiful. This book is open-access (i.e. it's free to read at this address) because I believe knowledge should be free. However, if you think the book is worth a few dollars (5€ or 10€), you can use Paypal to make payment. This money will help me to travel to Python conferences and to write other books as well. If you don't have money, it's fine. Just enjoy the book and spread the word about it.