http://commons.wikimedia.org/wiki/File:Microvessel.jpg?uselang=de
Schwarz-weiß-Foto Microvessel showing an erythrocyte (E), a tunica intima of endothelial cells and a tunica adventitia of pericytes. (CC BY Robert M. Hunt 3.0
http://creativecommons.org/licenses/by/3.0/deed.de