Abstract: The present invention relates to a cell culture device (1) for use with an optical microscope (40), comprising a housing (10) that is configured to be placed onto a stage of an optical microscope (40) in front of an objective (41) of the microscope (40), the housing (10) enclosing an internal space (11) of the housing (10), a removable flow chamber (2) enclosing an internal space (20) for accommodating a cell culture (CC) comprising living biological cells, a heater (3) arranged in the internal space (11) of the housing (10) for heating said fluid medium (M) to be guided through the flow chamber (2), a first flow path (P1) arranged in the internal space (11) of the housing (10) for guiding said fluid medium (M) towards the flow chamber (2) via said heater (3), and a second flow path (P2) arranged in the internal space (11) of the housing (2) for guiding said fluid medium (M) away from the flow chamber (2), and a pump (4) for pumping said fluid medium (M) through the first flow path (P1) into the internal spac