A new method for generation of gas bubbles from a micropipette has been developed. In this method, step pulses of gas pressure are used to inject micro-volumes of gas into a liquid. Both the size and number of gas bubbles produced can be controlled through pressure regulation, pressure variation, orifice diameter and pipette position. A theoretical model derived to predict the size of bubbles generated from a non-vertical micropipette agrees well with the experimental results. (C) 2007 Elsevier Ltd. All rights reserved.