PROJECT SUMMARY The Texas A&M University College of Dentistry maintains a vigorous and growing research program focused on three main areas: 1) mineralized tissue formation and destruction, 2) craniofacial development, and 3) neurobiology of pain. As the number and diversity of NIH-funded research projects has increased over the past several years, so has our need for research infrastructure. This application addresses a key point of that need with a request for funding to purchase a multiphoton (MP) laser scanning microscope. This instrument will allow us to image fluorescent probes deep within palate, bone, and tooth in a way that is impossible with our current equipment. It will be built around an inverted stage with an environmental chamber that will allow us to track the migration of cells in live tissue explants over long periods. Fibrillar collagens and enamel are the basis for mineralized tissue, and the unique ability of MP imaging to generate second harmonics in both will allow us view the intimate relationship of the bone and tooth matrices with the cells that produce them. The inclusion of multicolor confocal laser scanning capability on this MP scope means we will be able to observe multiple fluorescent cellular probes in cleared samples while simultaneously viewing the structure of their matrix niche with second harmonics. Our neurobiology faculty will use the deep imaging ability of MP technology to visualize brain tracts and synaptic connections in the pathways that transduce orofacial pain. Our investigators’ needs for this instrument fall under two main classifications. First are those who have been using expensive off-site MP instruments at fee-for-service facilities to advance the Specific Aims of their funded projects. Second are those whose funded projects would benefit greatly from MP imaging, but who have found it too impractical to incorporate without an instrument of our own. Both these categories are well represented in the Major User Group. Acquisition of this long overdue instrument will allow our already productive investigators better achieve the stated Aims of their grants and enable new advances that they could not otherwise achieve.