In a living body and cell, various biomolecules such as proteins, nucleic acids, and sugars function by interacting with each other. To understand their precise biological functions occurring within a cell, it is important to investigate the activities or behaviors of these target molecules in living systems, where all of these interactions with other biomolecules are maintained. Using organic chemistry, macromolecular chemistry, and protein chemistry, we design and synthesize functional molecules, apply them to image behaviors or activities of target biomolecules, and then regulate the functions of these targets by utilizing light.