When someone realize folding experiments in vitro, most of times, the time of construction of one protein is much larger than the time spent with in vivo reactions. This difference is done thanks to the in vivo presence of enzimes which catalyse the reactions of folding process. Peptide binds are accelerated by peptidil prolil isomerase which, throught subsequents twistings, allowing one favorable binding. Besides the enzimes which help folding process, different kind of others molecules are necessary for one better efficiency in proteins folding. In order to prevent proteins agregations, it is important one "isolation" of these from the enviroment where they are submersed. Classes of proteins known as "chaperones" play this vital hole, inhibiting non desirable bindings and not allowing reactions with the medium, which can damage folding process.