Funds are requested for the purchase of a multi-photon microscope to be conveniently located near two of the major Penn Institutes whose faculty will share the equipment. Some 14 users from the School of Engineering and Applied Science, the School of Medicine, and several campus institutes will use the equipment for biomedical and biomaterial research investigations. The new equipment offers significant advantages over existing equipment in imaging penetration depth, sensitivity, photodamage, and the ability to observe multiple fluorophores simultaneously. Specific studies include the effect of environmental stimuli on cells, the microscopic basis of biomaterial behavior, polymer behavior at interfaces, etc. The facility will be made available to researchers at nearby Universities.