Efforts in nonlinear control have led to the level of generality in ehich conceptual solutions exist for all systems affine in control and the disturbance, and constructive designs exist for a specific class of nonlinear systems - although broad in terms of physical relevance. This monograph presents the fundamentals of global stabilization and optimal control of nonlinear systems with uncertain models. It offers a unified view of deterministic disturbance attenuation, stochastic control and adaptive control for nonlinear systems. It addresses a large audience of researchers, students, engineers and mathematicians.