An emerging imaging technology, a miniaturized fluorescence microscope (miniscope), is likely to revolutionize neuroscience. The miniscope is a 3 grams, wide-field fluorescence microscope that can be implanted and carried by small animals, providing new versatile means to perform cellular-resolution fluorescence imaging of large populations of nerve cells in vivo. Notably, this technology makes it possible to visualize the activity of the brain in freely moving and behaving animals, a possibility only dreamt about ten years ago. The goal of our research program is to use this technology to decipher neural mechanisms of navigation and learning in the hippocampus. This technology has been, thus far, almost exclusively used to monitor activity in the brain of mice. One particular innovative aspect of our research is the effort to employ this technology to record brain-activity in an avian species (the Japanese quail) in addition to mice. Also, we are trying to pioneer the use of this technology to activate optogenetic tools, specifically light-gated NMDA receptors and photoactivatable activity probes. These will provide the means for all-optical interrogation of neuronal systems, a major aspiration in neuroscience.