Many workflows available in other Infrastructural Units of the National Facility for Structural Biology may require a rapid sample quality control verification (if not performed by the users) or a step of sample optimisation, for instance via size-exclusion chromatography just prior to experiments. These services, which differ from the full characterisation of the macromolecular sample because of their ancillary role with respect to other IU workflows, may only be requested in combination with such workflows.