Scattering amplitudes underpin much of our understanding of Quantum Field Theory on Minkowski and are essential for interpreting particle collider signals.
This talk will describe some recent attempts to develop an analogous description of scattering in (quasi-)de Sitter spacetimes, such as the early inflationary Universe. These cosmological amplitudes open up new ways to interpret the "cosmological collider" signals in the Cosmic Microwave Background, and to improve our understanding of how fundamental properties such as unitarity and causality are realised in QFT on dS.