Photobiology is that branch of biological science which studies the interactions of light with living organisms. Here are some examples of these interactions. . . Light is a necessary part of the process of photosynthesis - light is crucial for plant growth. Light interacts with cells in the retina of the eye, so that we can see.
Light is used to improve human health, a field of medicine known as photomedicine.
Phototherapy is the use of light to treat of a variety of conditions, including cancer, leukemia, jaundice of the newborn and many skin conditions. Some organisms, for example fireflies and luminous bacteria, give off light as a result of chemical reactions taking place in specialized organs in their bodies. The intensity of light at different times of day has effects on the bodies of animals and humans - for example on the production of certain hormones, vitamin D and maybe even on some aspects of behavior. Light can have bad effects on organisms, including humans - for example, too much exposure to sunlight can cause skin cancer as well as premature aging of the skin and the eye. These are just some of the effects of light on living things - photobiologists are involved in research which tries to understand how these interactions work, and, in the case of harmful ones, how organisms, including humans, can protect themselves against their harmful effects.