In c.15 bc, the Roman Vitruvius stated that a good building should satisfy three requirements: durability, utility, and beauty. ‘Does form follow function?’ examines utility and beauty. It explains that structures are naturally lazy because they contain minimum potential energy. Each piece of structure, however small or large, will move, but not freely as the neighbouring pieces will get in the way. When this happens internal forces are created as the pieces bump up against each other. Force pathways are degrees of freedom and the structure has to be strong enough to resist these internal forces along these pathways. Form-finding structures are exciting and innovative examples of the fusion of engineering and architecture.