Cytochrome c oxidase (CCO), is better described in the term electron transport chain complex 4. For every detail that is known about this, you should search for it. Youtube offers some graphical representations that make it a bit more tangible. During the fourth phase of cellular respiration (oxidative phosphorylation), specific wavelengths of red and short-wave infrared light break the bond between nitric oxide and CCO. This allows oxygen to bind to NADH, restoring the normal pathway for hydrogen ions to create the electrochemical potential that produces ATP (cellular energy). A simple way to think of this process is that photons are essentially charging your cellular batteries.