Phototherapy uses blue light to break down bilirubin in the skin of newborns with jaundice. Bilirubin absorbs light between 400-500nm, which causes it to change shape and become water soluble so it can be excreted in urine. Special phototherapy lights are placed close to the baby to lower bilirubin levels and prevent health issues. Nurses provide skin care for babies under lights and monitor fluids, temperature and bilirubin levels. Phototherapy is stopped once bilirubin drops to a safe range to avoid side effects like dehydration.