Blood vessel is an indispensable component that constitutes the circulatory system of our body to supply oxygen and nutrients to tissues and organs and also to take waste and carbon dioxide away from them. Not only the basic function, it also has been importantly recognized as the key element that it is closely related to the onset and progression of the well-known diseases, such as cancers, hypertension, Alzheimer’s disease, and many other metabolic diseases including diabetes. In this talk, I will introduce our photoacoustic endomicroscopy technique developed for the in vivo visualization of microvasculature targeting all possible biomedical applications in a broad scope. Due to the importance of blood vessel in biological systems, developing a related visualization technique (i.e., angiography) has been an important subject always in biomedical engineering and physics. However, existing angiographic techniques suffer from either slow imaging speed (MRI) or shallow imaging depth (confocal microscopy) and also require a dedicated contrast agent in most cases. In this respect, we expect that our technique could make a viable contribution to biomedicine because it can provide capillary- or organ-level visualization of vasculature at a much higher speed and also without the aid of a contrast agent. In this talk, several biomedical application examples that we have been conducting will be presented.