Living cells have been referred to as the test tubes of the 21st century. New bioactive reagents developed in our lab are designed to function in cells and living organisms. We have prepared enzyme inhibitors, sensors of biochemical pathways, chemically-altered proteins, and activators of gene expression. In addition, many of these agents possess the unique attribute of remaining under our control even after they enter the biological system. In particular, our compounds are designed to be inert until activated by light, thereby allowing us to control their activity at any point in time.