Pipette tip morphology during the pressure polishing process. (Top) Before any polishing. (Middle) After polishing while applying pressure. A blunt taper forms; the tip diameter narrows slightly but is still too large for recording cells <5 µm in diameter. (Bottom) After final polishing. After the midpolishing stage, the air pressure is turned off, and polishing continues to narrow the tip opening to a final size of ∼0.5 µm.