The aim of this special collection of papers on the theme of ""Advanced Welding and Micro Joining/Packaging for the 21st Century"" was to review and analyze the state-of-the-art concerning the welding and joining/packaging technologies which are essential to the production of structures ranging from the compact to the ultra-large. This extensive collection of 164 peer-reviewed papers will provide the reader with an unparalleled guide to the most up-to-date knowledge available concerning these fields.