The Atomic Interferometric Observatory and Network (AION) in the Beecroft Building in the Physics Department at Oxford UK and MAGIS at Fermilab, near Chicago, US will enable the search for ultra light dark matter as well as searches for new fundamental interactions. In addition, it will provide a pathway towards detecting gravitational waves from the very early Universe and astrophysical sources in the mid-frequency band ranging from several mHz to a few Hz which is largely unexplored at present. The project is part of UKRI's Quantum Technologis for Fundamental Physics programme supported by the Stratgeic Priorities Fund of UKRI and administered by STFC for EPSRC and STFC.