Light is essential to our health and wellbeing; it regulates our sleep-wake cycle. It can also help with our daily routines: from bright functional light to keep you energized and up your concentration level, to warm light that creates a cozy ambiance that helps you to unwind in the evening. Light is just one form of electromagnetic radiation, or electromagnetic waves. These waves are all around us and come in many sizes. The largest electromagnetic waves, with wavelengths from a few centimeters to over 100 meters are called radio waves.