The Cellular Imaging Program (CIP) at CMIR studies the in vivo fate of cells by non-invasive, three-dimensional imaging modalities to answer critical questions in immunology and cell biology. Our program currently has several areas of emphasis (1) leukocyte trafficking within the whole-body of living mice, including migration to target sites in nonlymphoid tissues, (2) the functional behavior of cells at target sites during the effector phase of the response and (3) stem cell trafficking and differentiation. We are comparing the behavior of immune cells that mediate protective vs. nonprotective responses, and are measuring the in vivo effects of therapeutic interventions that modulate these responses. The technologies used in this program are based on intravital confocal and multiphoton microscopy, as well as on macroscopic and mesoscopic imaging available through CMIR resources. The latter include fluorescent protein tomography (FPT), magnetic resonance imaging (MRI), single photon emission computed tomography/computed tomography (SPECT/CT), near-infrared fluorescence imaging (NIRF) and bioluminescence imaging (BLI). A new wave of intracellular multimodal imaging probes, developed at CMIR, allow us to investigate the in vivo behavior of cells in live animals through these different modalities. There exist close interactions with several immunology programs at Harvard Medical School and Harvard Stem Cell Institute.