This front matter contains the series editors’ preface, contents, abstract, and acknowledgements. This monograph summarizes the major developments on nuclear reactor thermal-hydraulics over the last fifty years, primarily for the water-cooled reactors, and provides a direction for the future thermal-hydraulic developments for water-cooled, including small modular reactors or SMR, and Generation IV reactors. eBook keywords: Nuclear reactor, thermal hydraulics, cooling systems, computational fluid dynamics, modular reactors, neutronics, coolant chemistry, nuclear fission, heat generation, reactor thermal hydraulics.