Two-phase microchannel cooling is one of the most promising thermal-management technologies for future high-power IC chips. Understanding the boiling process and the two-phase-flow behavior in microchannels is the key to successful implementation of a microchannel heat sink. This book focuses on the phase-change phenomena and the heat transfer in sub-150 nm diameter silicon microchannels, with emphasis on thermal measurement and modeling, and the impact of small dimensions on two-phase flow regimes. Scientists and engineers tackling thermal and MEMS problems will find the discussion in this book inspiring for their future design of microscale heat transfer experiments. This book will also contribute to the study of two-phase microchannel flows by providing extensive experimental data which are otherwise difficult to access.