The article focuses on the collection of papers presented at the Second International Conference on Microchannels and Minichannels, held in Rochester, New York, June 17-19, 2004. The conference was hosted under the joint sponsorship of the American Society of Mechanical Engineers and Rochester Institute of Technology. The first paper by highlights the research needs and application of advanced instrumentation, such as differential pressure measurements, current distribution and neutron radiography, in studying the water distribution in minichannel passages in PEM fuel cells.