The Fluorescence Microscope Holder 400 connects a Twist-on efocus Fluorescence Microscope Body and stereotaxic instrument during cannula implantation or head-fixed imaging. One holder's side is optically paired with the microscope's CM3 connector. At the same time, its other end features an FC receptacle for a 400 µm core fiber-optic connector that provides illumination to the connected microscope. The Clamp for Fluorescence Microscope Holder attaches the holder to a stereotaxic positioner.