Over the last several years our lab and our collaborators have pioneered a new area -- the development of fully genetically encoded reagents that, when targeted to specific cells, enable their physiology to be controlled via light. These reagents, known as optogenetic tools, enable temporally precise control of neural electrical activity, cellular signaling, and other high-speed natural and synthetic biology processes using light. As an example, light-sensitive 7-transmembrane proteins known as microbial opsins are found in organisms throughout the tree of life, where they mediate photosynthesis and light sensation. When genetically expressed in specific neurons in the brain, the targeted neurons can be activated (e.g., if they express the light-gated cation channels ChR2, etc.) or silenced (e.g., if they express the light-driven chloride and proton pumps Halo/NpHR, Arch, Mac, etc.) by pulses of light. Such tools are now in widespread use in neuroscience and bioengineering, for the study of how specific neurons contribute to processes ranging from cognition to emotion to movement, and to brain disorder states. These tools are being evaluated as components of prototype optical neural control prosthetics for ultraprecise treatment of intractable brain disorders. We continue to develop new kinds of optogenetic molecular tool, and to improve the performance of existing classes of tools, using genome mining and molecular engineering techniques, often in collaboration with genome sequencing collaboratives and basic molecular scientists. These reagents highlight the power of basic-science understandings of ecological diversity, in yielding new tools for understanding biological complexity and addressing human health. We distribute these tools freely to researchers, in collaboration with a number of outside institutions -- see the "Resources" pages below for up-to-date descriptions of these tools as well as how to get them, and the "Publications" pages for detailed information about, and demonstrations of use of, these tools.