The human brain is a highly complex system comprised of billions of cells, called neurons, that are all interconnected. Normal brain function depends on effective communication between neurons, which requires signals to travel down a nerve cell and then over to the next cell it is connected to. Several diseases result from impairments in the communication between neurons, which is why it is important to study these signals in the living brain. Since the living human brain is difficult to study, scientists use simpler organisms like mice. To see mouse neurons, a piece of skull is replaced with a clear glass window. Powerful microscopes can then be used to capture snapshots of neurons deep inside live brains! Clever use of lasers to excite chemical “tags” inside the neurons makes them glow with fluorescent light. Join us as we explore the inner workings of neuron communication in the living brain.