Our lab is interested in the mechanisms that underlie synaptic competition between neurons that innervate the same target cell. Such competitive interactions are responsible for sharpening the patterns of neural connections during development and may also be important in learning and memory formation. The Lichtman laboratory studies synaptic competition by visualizing synaptic rearrangements directly in living animals using modern optical imaging techniques. We have concentrated on neuromuscular junctions in a very accessible neck muscle in mice where new transgenic animals and other labeling strategies allow individual nerve terminals and postsynaptic specializations to be monitored over hours or months. In addition, we have developed several new methods to improve our ability to resolve synaptic structure. One new method is the “Brainbow” mouse, in which combinations of distinct fluorescent proteins are stochastically expressed in neurons, resulting in labeling with over a hundred unique hues that allow neighboring neuronal processes to be clearly distinguished from one another. Another technique we have optimized is serial electron microscopy reconstruction. For this we have developed a new device that makes possible automated ultrathin sectioning of large volumes of brain tissue (several cubic millimeters), called an Automatic Tape-Collecting Lathe Ultramicrotome (ATLUM).