"Understanding the thermal balance of the interstellar medium (ISM) is of fundamental importance for studying star-formation and the evolution of galaxies over the history of the Universe. The photoelectric effect is the dominant source of heat in the ISM and its efficiency is determined by the properties of interstellar dust grains (their abundance, size distribution and charge state, primarily). Our knowledge of this crucial process is currently mostly theoretical, due to the lack of necessary observational constraints. However, new observations obtained as part of the KINGFISH key program on the Herschel Space Observatory will now let us observationally test our theory of photoelectric heating in a diverse sample of extragalactic environments. In this proposed project, we will use a combination of state of the art observations from Herschel and its predecessor, Spitzer, to study the efficiency of photoelectric heating as a function of dust grain properties in a sample of nearby galaxies.The leader of this project, Dr. Karin Sandstrom, will carry out the research as part of the Galaxies and Cosmology group at the MPI for Astronomy. Dr. Sandstrom's expertise in infrared spectroscopy and dust physics make her the ideal leader for this project. The support and mobility provided by a Marie Curie Incoming International fellowship will ensure that this innovative research into the ISM of nearby galaxies is performed at an EU research facility and will facilitate the transfer of knowledge on infrared spectroscopy and dust physics to the MPIA nearby galaxies group."