Cellular signaling networks determine the fate and (dys)function of cells in response to a variety of environmental stimuli. The discovery of genetically encoded fluorescent proteins based biosensors over 2 decades ago enabled the detection and real-time measurement of cellular dynamics and signal transduction pathways with high spatial and temporal resolution. In this lecture, we will study how to engineer genetically encoded biosensors and chemogenetic/optogenetic tools and will also discuss many of the molecular designs that can be utilized in their development. We will also study how the high temporal and spatial resolution afforded by fluorescent biosensors can be aided for our understanding of the spatiotemporal regulation of signaling networks at the cellular and subcellular level. It is also planned to highlight some emerging areas of research in both biosensor design and applications that are on the forefront of biosensor development