The Cell Morphology Core is an independent service facility that provides a full range of services for morphologically based studies ranging from electron microscopy to complex image analysis. Services include preparation of tissues for microscopic analysis including paraffin embedding and sectioning, and cryosectioning. The Core also provides services for detection of transgenes and transgene products including in situ hybridization and immunohistochemistry. This core has a track record of interaction with the investigators on Projects 1, 2 and 6, and for the proposed PEGT, will also support studies outlined in Projects 3 and 4. This core has a track record of interaction with the investigators on Projects 1, 2 and 6, and for the proposed PEGT, will also support studies outlined in Projects 3 and 4. The core's major assets include its first-rate equipment and an interactive and knowledgeable staff. The core is structured so that core personnel can provide services on a fee-for-service basis, or if they prefer investigators an use the core's facilities to perform the studies themselves, with advice and assistance provided as needed by core staff. Because of the organizational structure already in place, this core is well-qualified to serve as a shared resource for all the PEGTs and for other NHLBI-funded investigators.