My team studies the role of Ca²⁺ and other intracellular signals in the digital and analogue control of cell activation, cell division, defense, and death. Calcium and other intracellular signals are fundamental to the control of all biological processes in animals, plants and micro-organisms. A rise in cytosolic free Ca²⁺ is the signal for all types of muscle contraction, neural conduction, secretion, certain cell cycle events, cell defense and death. The key to establishing this research program has been the development of techniques for measuring, imaging and manipulating Ca²⁺ and components of its signaling system in live cells. I have therefore developed bioluminescent and fluorescent probes to measure and image free Ca²⁺, kinases, and proteases in defined parts of live cells, including single cells and whole organisms, in the cytosol, endoplasmic reticulum (ER), nucleus and plasma membrane. These probes include a new set of genetically engineered proteins called Rainbow proteins that change color when they react with a substance of biological and biomedical importance. There are three types. Type 1 involves engineering two bioluminescent proteins together that emit different colors; e.g. firefly luciferase-aequorin monitors ATP by yellow light and Ca²⁺ by blue light simultaneously. In type 2 the reactive site is engineered into the bioluminescent protein. Type 3 depends on energy transfer; e.g. using aequorin or obelin as a donor and GFP as an acceptor with a reactive linker in between. They can then be quantified by measuring or imaging the ratio of light intensity at two or more wavelengths simultaneously.