Intravital microscopy (IVM) methods are enjoying an ever broader acceptance as they can be used to gain insight into cell biology in vivo. Unfortunately, most set-ups use window chambers (e.g. cancer) or isolated organs, all highly artificial model systems which are often not compatible with survival imaging. Because of these caveats, imaging in orthotopic locations is always preferable and can theoretically be achieved via motion compensation and tissue stabilization techniques. Recently, different approaches have been proposed including the use of suctioning devices for lung imaging. Unfortunately these approaches are not very effective in achieving stabilization. Moreover many of them induce severe damage to the myocardium. In this proposal we intend to develop a in-vivo real-time intravital microscopy imaging system for imaging moving organs (specifically the beating heart) at the sub-cellular resolution level, capable of compensating all motion artifacts inevitably present in in-vivo models. Our approach will use a combination of rigid motion stabilization through the design of novel stabilizers and sophisticated algorithms for acquisition during advanced cardiopulmonary gating. This system will allow for the first time to study in vivo the biology and physiology in the beating heart. This is at present a totally unexplored field due to the current lack of availability of any imaging technique. Results will be potentially exciting and innovative and will open a new paradigm in the understanding of the physiological properties of the heart and immune system responses.