The symbiosis of electrons and light forms the basis of life: The microscopic motion of electrons creates light which supplies our globe with life-giving energy from the sun. Electrons transform light into biological energy during photosynthesis and into biological signals endowing us with the capability of seeing the world around us. Upon their motion inside and between atoms electrons emit light, carry and process information in biological systems and man-made devices, create, destroy, or modify molecules and thereby affect biological function. Consequently, they are key players in physical, chemical or life sciences as well as information, industrial and medical technologies likewise.