The bottom-up construction and operation of machines and motors of molecular size is a topic of great interest in nanoscience and a fascinating challenge of nanotechnology. Research in this field is stimulated by progressive disclosure of the secrets of the natural nanomachines which constitute the material base of life. Examples of artificial nanoscale machines and motors have been built upon various types of molecular and supramolecular species like rotaxanes, catenanes, and DNA. In recent times, the evolution of the structural and functional design of such systems has led to the construction and operation of complex molecular machines that, in some cases, are able to do specific tasks.