Light energy goes into eyes stimulate photoreceptor in eyes. Light, as waves carry energy, contains energy by different wavelength The unique biochemistry of these complexes allows us to reliably and reproducibly collect continuous visual information about our environment. Moreover, other nonconventional retinal opsins such as the circadian rhythm regulator melanopsin also initiate light-activated signaling based on similar photochemistry Two-photon excitation as a tool for understanding the bio