A full-spectrum lamp is a device that emits light with a colour composition as close as possible to natural daylight. While conventional artificial lighting in homes or offices often contains only a limited part of the colour spectrum, typically with yellow or blue tones, full-spectrum light seeks to include all the colours of the rainbow in the proportions found in nature. The aim is to provide the human body with a light perception that is natural to it and to which it is evolutionarily accustomed. This light thus helps regulate an internal biological clock known as the circadian rhythm, which influences sleep-wake cycles, hormone production, mood and energy levels. The quality of such light is often described by its 'colour rendering index' (CRI), where a higher value means that colours look as natural under this light as they do in the sun. For safety, therapy lamps are equipped with filters that remove harmful UV rays.