The first step in creating human vessel mimics is to make iPS cells from skin, blood or cells in urine. In some cases these will be from patients with genetic diseases that affect vessels. The iPS cells can be turned into endothelial cells and pericytes (or mural cells) that are the cellular components of the vasculature. By carefully making different types of endothelial- and mural cells, it is becoming possible to create arteries, veins, capillaries or lymph vessels. These cells are then introduced into microfluidic devices where under conditions of flow they organize themselves into three-dimensional tubes, with an inner lining of endothelial cells and an outer layer of smooth muscle cells, just as vessels in the body. It is then possible, for example, to add immune cells to the circulating fluid in order to study the effects of inflammation on vascular integrity or interrupt flow to resemble thrombosis.