Unlike the large objects we see around us, tiny particles, including electrons, can sometimes act like objects and other times like waves. It's a mind-boggling idea physicists call "wave-particle duality." Scientists have even conducted special experiments to show this strange behavior. They found that when they tried to measure exactly where an electron is, it behaves like a particle, appearing in only one spot. But when they don't try to measure its position, it acts like a wave, spreading out and being in many places at the same time.