Form follows function

"form follows function" is a phrase associated with modern architecture. The phrase was coined by American architect LOUIS SULLIVAN. The original phrase is: form "ever" follows function.
  The principle behind this is that, the shape of a building or object should be primarily based upon it's intended function or use. For example, a building that is ment to be an office should have a formal look to it where as a recreational building should have a design that allows for the maximum achievement of its purpose.
  Modernism in architecture began as a disciplined effort to allow the shape and organisation of a building to be determined only by it's functional requirements instead of the traditional aesthetic concepts. It's applications range from architecture, to business models to automobile design and so on.