Since much of the life of cells is controlled by their chemistry, caged compounds can be used to intervene in this life in a myriad of specific ways. Organic chemists have synthesized the widest possible array of caged compounds for use by biologists. The smallest possible chemical unit (protons) to the "largest" (RNA and DNA) have been caged. Further, nonnatural products have been caged and used for blocking one aspect of cell function. Many caged compounds have been used for rapid activation of cell function, as uncaging often occurs in less than a millisecond. Studies with caged calcium and caged glutamate have proved particularly powerful in this regard. But will caged compounds continue into the second decade of the third millennium, their fourth decade? With the rise of other optical methods for control of cell function, are caged compounds still useful?