CERN has taken a decisive step towards the High-Luminosity Large Hadron Collider (HiLumi LHC) with the start of the cryogenic cooldown of its full-scale test facility to 1.9 kelvin (-271.3 °C). The 95-metre-long test stand replicates the advanced equipment that will progressively transform the LHC over the coming years and is designed to validate the new generation of beam-focusing magnets and their highly complex infrastructure. These systems form a cornerstone of the LHC upgrade scheduled to come into operation in 2030.