OASIS (Optical Activation, Stimulation, and Imaging Systems) are ground-breaking platforms for all-optical optogenetic stimulation and calcium imaging in vivo, both freely-behaving and head-fixed. With an OASIS, researchers can optogenetically and/or image stimulate single cells, multiple cells, and/or multiple areas simultaneously in the brain of an awake animal. The fully reconfigurable and futureproof design of the OASIS platforms makes them suitable for a wide range of in vivo applications, such as deep-brain stimulation & imaging, and cortical neural circuitry mapping etc.