This illustration highlights a review article on photolyzable caging molecules. The one shown above binds to (cages) zinc until it's hit with light at a particular wavelength, which leads to bond cleavage. With the molecule split in two, it no longer binds zinc. This is a neat trick for releasing zinc at a specific time and place as controlled by the researcher, and may be a particularly useful tool in neurobiology due to the role of zinc in the central nervous system. The products of photolysis are shown as having been taken out of commission, lying helplessly on the floor.