Optical control of calcium switches that orchestrate fast signaling in the brain. Cytoplasmic increases in calcium trigger enzymatic cascades responsible for synaptic plasticity in the brain. However, to date, genetically-encoded approaches to control calcium abundance, and the cognate enzymes calcium activates, are lacking. We will endow CaMKII, a kinase activated by calcium that is essential to memory formation, with optical control through unnatural amino acids. We also aim to enable rapid changes in cytoplasmic calcium through light-activated calcium-selective ion channels. By deploying these tools in neurons and their dendrites, this project aims to elucidate dynamic aspects of synaptic signalling in space and time.