Red fluorescent protein, also known as RFP, is a type of protein that emits red fluorescence under ultraviolet light. It is an essential optical imaging tool in the field of life science. RFP can be used for live cell imaging, marking protein expression, and various protein-related experiments. It is one of the most commonly used fluorescent proteins, along with green fluorescent protein (GFP) and orange fluorescent protein (OFP). RFP has several advantages compared to GFP. Firstly, RFP can be used in combination with GFP to address scientific issues that GFP alone cannot solve. Secondly, RFP has longer excitation and emission wavelengths, which results in a lower background during intracellular imaging.