The Mid-InfraRed Instrument (MIRI) on board the James Webb Space Telescope will be used by astronomers to study faint comets circling the Sun, newly born faraway planets, regions of obscured star formation, and galaxies near the edge of the universe. It must work at extremely low temperatures, of just 7 K above absolute zero or -266° C. Here, MIRI is being placed in the thermal test chamber at RAL Space, Oxfordshire, UK.