Fluorescence is a phenomenon where a substance absorbs light at a certain wavelength and then emits light at a longer wavelength. This process is commonly used in various scientific fields such as biology, chemistry, and physics for various applications, including imaging, sensing, and detection. Fluorescence is often used to label and track molecules in cells and tissues, to study protein interactions, and to identify chemicals in samples. The study of fluorescence involves understanding the properties of fluorescent molecules, the mechanisms of fluorescence emission, and the development of fluorescent probes and techniques for various research purposes.