Ordering (or controlling) chaos is a new concept, which has recently attracted much attention from the communities of mathematics, physics, engineering and biomedical and computer sciences. This publication offers an introduction to various successful methods for the control of chaos in nonlinear dynamical systems. The authors intend to present a self-contained, elementary and rigorous treatment of the subject, and to provide a firm basis for the further study and research in this rapidly developing direction, in the important field of nonlinear systems dynamics and control.