Photoreaction is a chemical process that occurs when light energy is absorbed by molecules, leading to a change in their structure or energy state. This process is essential in various natural phenomena, such as photosynthesis, where plants convert sunlight into chemical energy. In photoreaction, light typically excites electrons in a molecule, allowing them to move to a higher energy level. This can result in the formation of new chemical bonds or the breakdown of existing ones. Photoreactions are also utilized in technologies like solar cells and phototherapy, showcasing their importance in both nature and human applications.