PURPOSE: Optogenetics is an invaluable tool to study brain circuits, but typical systems rely on tethered approaches to deliver light to the brain that hinder natural behavior. With the increasing prevalence of complex behavioral phenotyping in neuroscience experiments, wireless devices for optical stimulation offer great promise to overcome these limitations. METHODS: In this work we critically review recent systems engineering and device design approaches to deliver light to the brain with wireless operation for optogenetic experiments. RESULTS: We describe strategies used for wireless control and communication, wireless power transfer, and light delivery to the brain with a focus on device integration for in vivo operation in freely behaving mice. CONCLUSION: Recent advances in optoelectronic systems, material science, and microtechnology have enabled the design and realization of miniaturized wirelessly-controlled optical stimulators for true untethered experiments in rodent models.