Recent advances in Micro Air Vehicles have produced impressive results for platform weighing below 50 g. The lightest platforms to take flight with a minimum of functionality are below 0.5 g, but researchers dream of flying at insect size. However many difficulties occur when scaling down existing technologies. Aerodynamic laws equate to decreased efficiency at smaller sizes and hence more power per weight is required. Current energy storage technologies do not have the required capacity and power-trains are no longer efficient enough. Construction is difficult due to small size and low weight requirements. This chapter surveys the status of current technology and its prospects in miniaturization, and shows several examples to illustrate the state of the art and the difficulties in reaching ever-smaller platform sizes.