In order to efficiently tackle the multiple conditions falling within the scope of rare and complex skin conditions, the 56 centers of the ERN-Skin cooperate through 9 thematic groups, each coordinated by one or several chairs. Although distinct, the fields of these groups often overlap, leading them to share their expertise on a daily basis, as knowledge about rare skin disorders progresses. The advances in the understanding of one group of these rare diseases are essential for the others.