The transition from macro to micro-sensor systems in the last decades has been made possible by the use of silicon and by development of micro-technology. Semiconductors opened the door to the realization of sensors based on Very Large Scale Integration Systems in which the external information is transduced into an electrical signal managed directly inside the micro-devices by the use of microelectronics. Up to now, the most powerful integrated systems may be considered the Medipix chip for medical imaging and avalanche photodiodes operated in Geiger mode (SiPMs) for photon radiation detection. A similar transition from micro to nano is now knocking at the door. New nanotechnologies allow the realization of finely pixelled surfaces and manipulation of nano- structured materials at a few nanometer scales. Sensors can be created by flipping from a top-down process to a bottom-up approach. To do this …