PROJECT SUMMARY. High-sensitivity and microscale resolution instruments are essential for groundbreaking biomedical research. In vivo imaging technologies are particularly valuable to measure complex biological processes in live animals and track them over time, such as cancer metastasis, volume distribution of novel drugs and tissue homing of stem cells after transplantation. Optical imaging, in particular, has become extremely sensitive with the development of very efficient fluorescent dyes and nanoparticles as well as luciferase-based bioluminescence tools. In vivo spatial targeting of optical signals through the development of transgenic animals and cells that are engineered to express fluorescent or bioluminescent reporters, in both inducible and conditional manners, have enabled unprecedented in vivo applications of optical imaging in a variety of research fields. This shared instrumentation proposal is to purchase the optical IVIS SpectrumCT system (PerkinElmer), which will operate within the Metabolic Phenotypic and IVIS Core (Animal Phenotyping Core) in the Boston University Medical Campus. This Core has been successfully operational since 2011 and currently offers technical support for this instrument to 18 NIH-funded principal investigators. A variety of groundbreaking research projects has been conducted with the use of the Animal Phenotyping Core’s IVIS over the years, including the development of novel cargo nanoparticles for drug delivery, the discovery of molecular targets of cancer progression and metastasis, the optimization of tissue homing and organ regeneration with pluripotent stem cells. The new SpectrumCT is a high-sensitivity optical imaging platform with integrated micro-computed tomography for 2D and 3D bioluminescence and fluorescence detection and radiographic (CT) imaging. This state-of-the-art instrument will replace our current IVIS, which is no longer supported by PerkinElmer, while providing enhanced capabilities for monitoring and quantifying biological processes longitudinally in up to 10 live animals. This new generation IVIS provides fast multi-imaging modality combined with low dose CT, enabling co-registration and spectral unmixing for advanced 2D analysis and 3D reconstructions. In addition to ongoing projects, the new IVIS SpectrumCT will be used by additional NIH-funded users to advance their research on bone development, the effect of obesity on breast cancer, novel antibiotic therapeutics and other groundbreaking research projects. Importantly, the availability of this in vivo instrumentation will complement ex vivo imaging and quantitative modalities, such as confocal microscopy and FACS, currently available in the core facilities across the entire Boston University community, expanding the high-end instrumentation toolset crucial for the success of research investigators.