Early in the last century, scientists found that light has the characteristics of both waves and

Particles ! These "light particles" became known as PHOTONS, and the concept is known as "wave-particle duality". In fact, Sir Isaac Newton et al were also thinking along similar lines  hundreds of years ago. 
The photo electric effect is often cited as an experimental verification of PHOTONS and so also wave particle duality. There is also the case that ELECTRONS can sometimes be considered to be particles, and some times as waves. A european physicist de Broglie got, I think, a Nobel Prize for "wave particle duality"..