Have you ever seen lights turn on automatically when you step into a room? Or have you ever wondered how a garage door knows to not close when someone is standing beneath it? What these and countless other electronic devices have in common is a sensor. But how do sensors work? What are they used for? Discover how robotic and electronic sensors can be programmed to work as our five senses do. Learn how sensors are used to save energy, keep us safe, and sometimes make life a little more convenient! Victoria G. Christensen is a geologist and a hydrologist with over 20 years of experience, who writes on a variety of scientific and engineering topics for children. She lives in Fargo, North Dakota, with her husband and three great kids.