I found this meme on reddit while searching, and I learned a bit more about photosystem II (PS2). Photolysis is one of the many terms used to describe the phenomenon by which light energy can degrade and/or split molecules. It is essential in photosynthesis, because in PS2 it is utilized to split water molecules, thereby sourcing protons to drive ATP synthesis. Source: https://www.reddit.com/r/biologymeme/comments/1h0qjnl/a_bit_obscure/