Over the last decade, there have been remarkable technological advances that have revitalized the age old idea that biology is first and foremost an observational science. Nowhere has this Galisonian ideal of scientific discovery been more realized than in the study of cell biology and signaling processes that govern a cell’s functionalities. Imaging techniques, beginning with the advent of genetically encoded fluorescent proteins, to the more recent single molecule imaging techniques that allow for observation of biological processes at resolutions below the diffraction limit of light, have given scientists the ability to gaze deep into living cells and discern molecular processes. These technologies have more than ever illustrated that the cell is not merely an aqueous mixture of proteins and molecules enclosed in a lipid bilayer membrane, but rather a tightly organized structure where signaling processes can be highly anisotropic. Detailed observations of cellular processes, afforded by these new imaging techniques, have given rise to a host of new questions regarding the orchestrating mechanisms underlying complex signaling events, the answers to which require precise perturbations that induce very specific and controlled changes. Given the complex spatial organization of the cell cytoplasm and the strict temporal order of molecular signaling events, traditional experimental methods to probe and dissect cellular signal transduction suffer from major drawbacks. Genetic manipulation techniques such as knockdown, overexpression and mutation, while powerful for identifying important proteins in a given signaling circuit, are often slow and pleotropic in their effects and therefore lack the spatiotemporal specificity needed to make predictive spatial and temporal models of signaling networks. Small molecule inhibitors, when there’s good target specificity, can act fast but lack inherent spatial control due to their rapid diffusion throughout the cell cytoplasm. Light-gated protein modules and other molecules offer both spatial and temporal control of proteins’ subcellular localization and functions. Recent years have witnessed a rapid expansion of these technologies which have already begun to produce spectacular advances in the understanding of cell biology, animal physiology, and behavior. This thesis is written in two parts. The first part, consisting of one chapter, gives an overview of the current light-gated technologies to control protein functions. The second part which is divided in two separate chapters describes the development and testing of two novel technologies that make use of light to control cell surface receptors activation in a spatiotemporal specific manner. These chapters will also discuss the potential applications of these technologies to address outstanding questions in cellular signal transduction.