A cranial window with an accessing port for medical research includes a sheet-shaped member configured to be installed as a cranial window on an outer brain skin of an animal subject through an opening in a skull, the sheet-shaped member having an optically transparent window therein or in entirety thereof to allow optical imaging into a brain of the animal subject; and an access port in the sheet-shaped member for allowing sterile insertion and removal of an accessing member having a sharp tip, the access port being configured to be self-sealing when the accessing member is removed.
