The electromagnetic properties of metamaterials can be engineered to achieve substantially more flexibility and variety than those available from conventional materials. Adding some degree of external control or power to metamaterials enables another level of functionality. We describe our recent efforts to develop an approach for realizing powered and nonlinear metamaterials in which each unit cell contains embedded active or nonlinear elements. We demonstrate experimentally how such active and nonlinear metamaterials enable properties such as gain, nonreciprocity, and phase conjugation. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).