Vitamin D is primarily produced by the human body when exposed to sunlight. When UV rays hit the skin, a chemical reaction occurs that converts a cholesterol derivative into vitamin D3, which then is transformed into a usable form of vitamin D in the kidneys and liver. Vitamin D plays a crucial role in calcium absorption, promoting bone health and supporting the immune system. It is also essential in regulating mood and may have a role in preventing chronic diseases. Given its importance, many people are encouraged to get adequate sunlight exposure or consider supplements, especially in areas with limited sunlight.