A single-cell microbeam is a narrow beam of radiation, of micrometer or sub-micrometer dimensions. Together with integrated imaging techniques, microbeams allow precisely defined quantities of damage to be induced at precisely defined locations. Thus the microbeam is a tool for investigators to study intra- and inter-cellular mechanisms of damage signal transduction, and RARAF provides a variety of state-of-the-art microbeams for our collaborators. With 29 outside collaborators, we describe 30 collaborative / service-based research projects, which both drive and utilize our technological developments;all the projects are logical outgrowths of currently-funded peer-reviewed research. The two main collaborative research themes relate 1) to studies involving single cells, and 2) to studies involving 3-D tissues and small animals - for systems-biology based studies of microenvironment effects. The proposed core technology developments focus on four user-identified areas: 1) further extended technologies for the microbeam itself, including the first neutron microbeam;2) new single-cell manipulation technologies, with an emphasis on microfluidics-based approaches;3) enhanced imaging technologies, with an emphasis on reducing the amount of UV and stain required for imaging;4) microbeam irradiation technologies for small-animal systems. We will continue ongoing training of users at all levels, from undergraduate to senior faculty. RARAF has de facto become a training center for developers of new microbeams, worldwide, and we will formalize this with a new training course at RARAF entitled "Single-Cell Microbeams: Theory and Practice", which will involve formal lectures, extensive hands on experience, as well as technology transfer options. The RARAF web site is a significant repository of information about microbeam technology and results;we will expand this further by creating an online microbeam educational resource. This resource will feature a podcast- and web-based virtual microbeam training course that is based on our new training course, a microbeam wiki, and a microbeam blog. We are heavily involved in the upcoming International Workshop on Microbeam Probes of Cellular Radiation Response in Japan;the 2012 meeting is scheduled to return to us at Columbia University. PUBLIC HEALTH RELEVANCE: A single-cell microbeam is an extremely narrow beam of radiation which allows biological damage to be induced at precisely defined locations within cells. Microbeams probe the way that information about DNA damage is transmitted from one location to another in cells or tissues - which, for example, is proving critical in understanding the risks associated with low levels of ionizing radiation.