Ex vivo (Latin: out of the living) means that which takes place outside an organism. In science, ex vivo refers to experimentation done in or on living tissue in an artificial environment outside the organism. The most common "ex vivo" procedures involve living cells or tissues taken from an organism and cultured in a laboratory apparatus, usually under sterile conditions for a few days or weeks. This allows experimentation under highly controlled conditions impossible in the intact organism, albeit at the expense of looking at the tissue in its "natural" environment. One widely performed ex vivo study is the chick chorioallantoic membrane (CAM) assay. In this assay, angiogenesis is promoted on the CAM membrane of a chick embryo outside the organism (chicken). Ex vivo studies are usually performed in vitro, although the use of these two terms is not synonymous.