In addition to the animation activities of the scientific and engineering poles, the role of the transverse groups is to encourage interaction between teams and services from different poles. Their scope is a set of projects/activities on a theme that is by nature transverse to the poles. Created for three years by decision of the Directorate, they each have one or more leaders and abudget. These groups may be more scientific in nature, in which case they are similar to the CNRS GDR (Groupements de Recherche), or they may have a strong technical connotation, involving a large number of technical staff from the engineering and accelerator poles or platforms.