The OASIS Fiberscope System is a flexible, high-throughput in vivo cellular-resolution imaging system designed for freely behaving animal experiments. Its lightweight, fiber-based architecture scales from single-region imaging to multi-region, multi-animal imaging, while supporting precise synchronization of neural activity with behaviour. Integration with the Polygon DMD Pattern Illuminator enables targeted optogenetics and cellular-resolution imaging, providing spatially precise stimulation alongside real-time fluorescence imaging for advanced neuroscience research.