Spectroscopy is the study of the absorption and emission of light by atoms and molecules, and how this relates to the wavelengths of light. It is a science of the spectrum, a set of energy bands of varying wavelengths (colours) produced by electromagnetic radiation. It is typified for a visually oriented species like humans by the rainbow band of colours that emerges when you pass white light through a prism (or sunlight through raindrops). This property of light became the domain of Isaac Newton in the late 17th century. In his 1704 masterpiece of theoretical dualism, Opticks, Newton defined many of the ground rules 200 years before spectroscopy was first seriously applied.