Jacques Lemonnier, best known as Jak, studied fine arts in Le Havre and cooperated on several fanzines and local projects. In 1983, he participated in the collective album 'Le Neuvième Cauchemar' for publisher Ludovic Trihan, using the pseudonym Jakez Bihan. From 1985, his work appeared in magazines like Censuré and Fluide Glacial. He worked with scriptwriter Jacques Lerouge on 'Harrison Pigeot', and under the pseudonym Jacobsen, he produced various erotic albums in a 1960s American underground style between 1987 and 2002 (a.o. 'La Grenouille', ' Mathilde et Gilda', 'Le Loup et l'Agnelle' and 'Céline').
Additionally, Lemonnier made children's books and created the gag series 'Léo et Lu' with Georges Grard, using the signature Jak for the first time. For Petit à Petit, he began a second series, called 'Robinson' in 2003.