This book summarizes very recent developments - both applied and theoretical - in nonlinear and nonsmooth mathematics. The topics range from the highly theoretical (e.g. infinitesimal nonsmooth calculus) to the very applied (e.g. stabilization techniques in control systems, stochastic control, nonlinear feedback design, nonsmooth optimization). The contributions, all of which are written by renowned practitioners in the area, are lucid and self contained. Audience: First-year graduates and workers in allied fields who require an introduction to nonlinear theory, especially those working on control theory and optimization.