Research and education in a wide range of studies involving micro/nanoscale heat and mass transfer have advanced the state-of-the-art rapidly over the past decades primarily due to technical advancements that provided the ability to manipulate materials precisely at the atomic/molecular level which has enabled the development of materials with novel properties. These advancements have significantly impacted the scientific and technological frontiers in the fields of energy and medicine. The studies have exhibited extremely rapid progresses in both fundamental understanding and industrial applications, especially in the areas of thermal management, drug delivery, and therapy. For example, stable colloidal solutions obtained by doping various solvents with minute concentration of nanoparticles (also called “nanofluids”) have attracted considerable attention in contemporary research due to their perceived superior heat transfer properties such as thermal conductivity and convective heat transfer. The number of research articles dedicated to this subject has been experiencing an exponential increase in the last decade [1], which has advanced the knowledge about the basic mechanisms responsible for their apparent superior transport properties such as the critical rheological behavior of nanofluids. These advancements also bear great promise in various industrial applications, such as for the developments of novel coolants (or heat transfer fluids, HTF) in heat exchangers, electronic cooling systems, automobile radiators, and concentrating solar power systems. Meanwhile, nanotechnology applications in medicine have also garnered significant attention in the research communities which has led to a fast growth in research activities and has resulted in many exciting discoveries. Four NIH sponsored nanomedicine centers were established in 2005 and hundreds of nanotech-based drugs and delivery systems have been developed worldwide. Sales of products developed using nanomedicine technologies reached over $6.8 billion in 2004, which involved over 200 companies and 38 products worldwide [2]. Moreover, an Alliance for Nanotechnology in Cancer has been established by the National Cancer Institute to accelerate the advances in nanomedicine revolutionaries of diagnostics, drug delivery, gene therapy, and many clinical applications.This special section is dedicated to the publication of recent developments of nanotechnology in energy and medicine applications, with the intention to provide yet another platform for researchers, educators, and practitioners around the world to exchange ideas on the state-of-the-art research and development and to identify future research needs in the interdisciplinary emerging fields of nanotechnology in energy and medicine. We would like to extend our sincere thanks to the authors for their contributions, especially their precious time and efforts invested in the special issue. We sincerely appreciate the service provided by the reviewers in improving the technical quality of the submitted manuscripts and therefore the impact of this journal. Finally, we are deeply grateful to the critical support and patience of general editor and his office staff during the whole process.The Research papers in this issue will be published in Vol. 4, No. 4 and Vol. 5, No. 1 of the journal due to different submission and processing stages.