Endothelial cell biology has developed into a vibrant discipline and has become a critical instrument to study several disease processes on the cellular and molecular level. It is now widely recognized that dysfunctions of normal endothelial cell homeostasis are involved in some of the most important human diseases, including ischemic heart diseases, hypertension, atherosclerosis, tumors, diabetes, arthritis, and inflammation. Further, the increasing importance and recognition of the field of vascular biology in general requires in vitro and in vivo techniques in order to address the complex questions.