The article elaborates an itinerary of the place that body has in Foucault's work. For this we study and discuses some of the principals Foucault's precedents like Nietzsche' and Canguilhem. The first one opens the possibility of connecting with a genealogical philosophy where the body is permeated by the history. The second one, shows how the problem of the body is permeated by a series of discussions about life that life's sciences had developed during the modernity. This allows to show how, far from the idea of a pure and receptive body unable to opposite to power, in Foucault's philosophy body is a permanent reservation of unpredictable forces.