This protocol describes an easy method for calibrating micropipette tips that have been pulled in the laboratory. It is essential to estimate the internal diameter of the pulled micropipette tip when adjusting parameters for a new puller or new type of glass tubing. A tip diameter of ~0.3 µm is optimal for the microinjection of mammalian cells in culture (e.g., CHO, PtK1, and COS-7). A 10% increase in diameter increases the delivery rate by more than 30% and can cause cell damage.
