To study the neural circuitry, the action of one cells under the context of others, one would precisely measure and perturb specific neuronal populations and molecules in behaving animals who are specifically engaged in performing the computation or function of interest. The dataset of millions of neurons firing together underlying a behavior are required to develop and refine theories (hypotheses) explaining animal behavior in terms of brain physiology. A key challenge has been difficulty of assessing the synaptic transmission with optical methods. My lab has developed a new suite of genetically encoded indicators that would enable one to 1) specifically highlight the structure of single spines and axonal termini in densely labeled neurons and record glutamate activity; 2) simultaneously record synaptic connectivity and glutamate activity to identify active synapses; 3) direct record the release of neuromodulators. We demonstrate the utility of these indicators in cells, rat hippocampal neurons and in vivo. We expect that applications of these imaging tools will contribute to a dynamic and comprehensive view of synaptic transmission in action to decipher the codes for transferring information across neural circuitry and systems.