The Facility for Antiproton and Ion Research (FAIR) near Darmstadt, Germany, has been under construction since 2012. One of the world’s most complex structures for cutting-edge research, it features a ring accelerator with a circumference of 1.1 km (0.68 miles) and 14 adjoining research buildings with laboratories, workshops, cooling systems, energy supply, and a high-performance computing centre. FAIR will supply matter of unprecedented density and temperature, and accelerate particles to nearly the speed of light, enabling vital research into matter and states that do not occur naturally on Earth. The architecture of this mega-project was designed by ion42, a joint venture between German architecture firms DGI Bauwerk (Berlin) and schneider+schumacher (Frankfurt am Main).Form Follows Beam provides deep insights into the genesis and execution of this extraordinary and spectacular architectural task, lavishly illustrated with plans, drawings and sketches, visualisations, and photographs. In conversation, architects and engineers speak about the evolution facility’s shape and why careful architectural and landscape design is essential even for a facility so strongly determined by technical requirements. Supplementary essays explain how FAIR works and what is being researched in it, and what makes Darmstadt its ideal location.