Although all the recent technological gallop brings undeniable advantages and increased comfort for all users, the problems related to the negative effects that a basic utility such as lighting, can have on the environment and astronomy, have begun to emerge and be brought up for discussion in forums, committees, specialized associations. The pressure on addressing this topic came from researchers who identified and demonstrated step by step the links between excessive outdoor lighting and specific dysfunctionalities of the ecosystem and between indoor lighting (including screen light) and certain health problems of the population. This book will explain the factors that generate light pollution, its quantifiable effects and possible measures that can be taken to optimize lighting systems in order to reduce pollution.