The possible reduction of mechanical devices to molecular length scales provides many exciting possibilities for enhanced speed, device density, and new functionality. Optical actuation of nanomechanical systems through the conversion of light to mechanical motion is particularly desirable because it promises reversible, ultra-fast remote operation. Past studies in this area have mainly focused on solution-based molecular machine ensembles, but surface-bound photomechanical molecules are expected to be important for future applications in this area.