Schematic drawing of the SEPIA instrument. A new instrument attached to the 12-metre Atacama Pathfinder Experiment (APEX) telescope at 5000 metres above sea level in the Chilean Andes is opening up a previously unexplored window on the Universe. The Swedish–ESO PI receiver for APEX (SEPIA) will detect the faint signals from water and other molecules within the Milky Way, other nearby galaxies and the early Universe. This diagram shows a three-dimensional view of SEPIA. Red areas show light being reflected off mirrors of different sizes and orientations, which direct the light from the telescope's antenna towards the detector. The right half of the diagram shows SHFI, another instrument attached to APEX.