This book provides a comprehensive summary of using computational tools to describe fluid flow in micro and nano configuration. This new version of the original book now covers length scales from Anstroms to microns (and beyond), as it contains many new developments and updated information throughout. The authors have maintained the emphasis on fundamental concepts with a mix of semianalytical, experimental and numerical results, and have outlined their relevance to modeling and analyzing functional devices. The material is divided into the three main categories of gas flows, liquid flows, and simulation techniques. It is appropriate for researchers in fluid mechanics interested in this new flow field as well as for electrical or mechanical engineers or physicists who need to incorporate flow modeling into their work.