The word innovation is usually applied to a new idea. But innovation can also be a new application of an old idea - and that is exactly what happened with the exhaust-blown diffuser, arguably the defining design concept of the 2009-2013 rules cycle.
The shorthand term really refers to the way in which high-speed exhaust gases were used to generate downforce. This involved variously blowing the diffuser, downforce-producing brake ducts and the way in which the airflow could be used to make the aero at the rear of the car work more effectively, for example by creating 'virtual' skirts.
But the idea of using exhaust gases for performance is far from new. Back in 1983, Renault introduced the concept by blowing exhaust gases directly into the diffuser (see bottom) in a way that was no longer possible once rules preventing running exhaust pipes through the floor came in.