The Twelfth Heat Transfer Photogallery was sponsored by the K-22 Heat Transfer Visualization Committee for the 2007 International Mechanical Engineering Congress and Exhibition (IMECE) held in Seattle, Washington on November 11–16, 2007. The peer-reviewed evaluation process for the presented entries identified the seven entries from 2007 IMECE and two additional entries from 2007 ASME Summer Heat Transfer Conference, held in Vancouver, Canada, for publication in the ASME Journal of Heat Transfer August issue of 2008.

The purpose of publishing these entries is to draw attention to the innovative features of optical diagnostic techniques and aesthetic qualities of thermal processes. To focus on visualization images and schematics, the text is kept to a minimum and further details should be found directly from the authors. My wish is that the journal readers enjoy viewing these collections, acquire knowledge of the state-of-the-art features, and also promote their participation in the 2008-IMECE Photogallery [http://www.asmeconferences.org/congress08].

The Call for Photogallery for 2008-IMECE is also announced in this issue of Journal of Heat Transfer.