As an emerging research field, nanofluids have sparked immense interest from researchers around the world and have been a subject of intensive research in recent years. Because of their fascinating thermophysical properties and heat transfer performances, as well as enormous potential applications, nanofluids are considered the next generation heat transfer fluids. This book covers a wide range of topics from preparation methodology, properties, and theories to applications of nanofluids. In addition to the state-of-the-art reviews and analysis on the key areas of nanofluids including thermophysical and heat transfer properties of carbon nanotube and magnetic nanofluids, viscosity of metal oxide nanofluids and pool boiling of nanofluids, this book presents extensive experimental and theoretical research efforts on thermal conductivity, viscosity, convective heat transfer, capillary wetting, and transport properties of nanofluids. Studies on the application of nanofluids in droplet-based microfluidic technology are presented. Another new area of nanofluid-based optical engineering is explored in this book. It also introduces a new class of nanofluids named-ionanofluids. Featuring contributions from some of the leading researchers in the field, this book is a unique reference source and an invaluable guide to scientists, researchers, engineers, industrial people, graduate and postgraduate students, as well as academicians across the science and engineering disciplines.