The endothelium is an excellent example of where biology meets physics and engineering. It must convert mechanical forces into chemical signals to maintain homeostasis. It also controls the immune response, drug delivery through the vasculature, and cancer metastasis. Basic understanding of these processes is starting to emerge and the knowledge gained from research is now being used in applications from drug delivery to imaging modalities. This book reviews current knowledge in mechanobiology of the endothelium and its implications for the development of theranostic devices.