26Plants utilize several families of the photoreceptors to fine-tune growth and development over a large range of environmental conditions. Among them Phytochrome is one of the families of photoreceptors or pigment sensitive to light in the red and far-red region of the visible spectrum. Phytochrome display both unique and overlapping roles throughout the life cycle of plants, regulating a range of the developmental processes from seed germination to maturation. The chapter summarizes the structure, interconvertable forms, phosphorylation, functional domain, interacting proteins, and physiological responses of phytochrome. Furthermore, it describes the role of phytochrome in various physiological processes occurring in plants such as flowering, shade avoidance, and sustainable crop production.