Observations of certain features of light challenged the particle model of light. Studies by Christiaan Huygens and Francesco Grimaldi pointed to an alternative picture of light as wave motion. Two characteristics of wave motion are wavelength and frequency, the product of which is the speed of the wave. In the 19th century, James Clerk Maxwell showed that light can be considered as very high-frequency oscillations of the electromagnetic field. ‘Waves’ considers the important light features of interference, diffraction, and polarization and shows how they have been exploited in the production of holograms and 3D images, super-resolution imaging, long-distance communication, and sunglasses.