Between 1865 and 1870, Peirce works on the concept of form, starting from Kant. According to Peirce, the form is “the respect in which the representation might stand for a thing”. The question of form is therefore deeply linked with the concept of aspect, because the form is the way in which the object presents itself through its qualities. The essay tries to show the way in which Peirce operates a semiotization of the aspect through the elaboration of the concept of form. Such semiotization consists in a displacement of the qualities of the object from the passive and neutral ground of perception to the productive e “informed” ground of representation.