The Primeval Structure Telescope (PaST), also called 21 Centimetre Array (21CMA), is a Chinese radio telescope array designed to detect the earliest luminous objects in the universe, including the first stars, supernova explosions, and black holes, in the range of 100 to 1 billion years ago. All of these objects were strong sources of ultraviolet radiation, so they ionised the material surrounding them. The structure of this reionisation reflects the overall density structure at the redshift of luminous-object formation.