This twelfth volume in the Poincaré Seminar Series describes recent research on the fascinating topic of chaotic dynamics in different contexts. It contains the following chapters: Étienne Ghys, The Lorenz Attractor, a Paradigm for Chaos Stéphan Fauve, Chaotic Dynamos Generated by Fully Turbulent Flows Uzy Smilansky, Discrete Graphs - A Paradigm Model for Quantum Chaos Paul Bourgade and Jonathan P. Keating, Quantum Chaos, Random Matrix Theory, and the Riemann Zeta-function Hans-Jürgen Stöckmann, Chaos in Microwave Resonators Stéphane Nonnenmacher, Anatomy of Quantum Chaotic Eigenstates Jacques Laskar, Is the Solar System Stable? Dating from their origin in lectures to a broad scientific audience these seven chapters are of high educational value. This book is of general interest to both physicists and mathematicians.