The 6th ASME Micro/Nanoscale Heat and Mass Transfer Conference (MNHMT 2019) was held in Dalian, China, July 7—9, 2019. The Conference was organized by Dalian Maritime University and Dalian University of Technology and sponsored by the ASME Heat Transfer Division. This conference series is dedicated to Dr. Chang-Lin Tien (1935–2002), the former chancellor of University of California, Berkeley, California. His intellect and unique vision continue to inspire our efforts in expanding the frontiers of micro/nanoscale heat and mass transfer. The previous five conferences were hosted by the National Cheng Kung University in Tainan (January 2008), Shanghai Jiao Tong University in Shanghai (December 2009), Georgia Institute of Technology in Atlanta (March 2012), the University of Hong Kong in Hong Kong (December 2013), and Nanyang Technological University in Singapore (January 2016).

Research and education on micro/nanoscale heat and mass transfer have advanced rapidly over the last three decades through many dedicated individuals and team efforts, which have made outstanding contributions to this field in both science and engineering. This conference provides an opportunity for researchers, educators, and engineers around the world to exchange ideas on the state-of-the-art research and identify future research needs in this emerging field. For this conference, we had 331 presentations including featured 18 plenary speeches and 31 invited talks, which span over 17 tracks and 51 sessions covering core areas of interest to our research community.

The papers selected from those presented at the conference were reviewed following the criteria set by the ASME Journal of Thermal Science and Engineering Applications and are published in this special issue. These papers reflect the contemporary research and findings in a broad spectrum of micro/nanoscale heat and mass transfer with both fundamental and applied research by theoretical, numerical, and experimental methods. It is hoped that these papers will serve as valuable references for fundamentals and applications of thermal and fluid transport phenomena at the micro/nanoscales. We would like to thank the Board of Conference, International Advisory Committee, Technical Program Committee, Organizing Committee, and all the Track and Session Chairs for promoting and organizing the conference. Thanks are also extended to all of the reviewers who have provided their critical comments. Special thanks are owed to the Journal’s Editor Srinath Ekkad, who has provided tremendous encouragement and support in making this special issue possible.