“When Henry Ford made cheap, reliable cars, people said, ‘Nah, what’s wrong with a horse?’ That was a huge bet he made, and it worked.” – Elon Musk.
Grid Fins – Russia invented grid fins for air to air missiles in the 1950’s (Missile Grid Fins, Aerospaceweb.org). See the grid fins on the rear section of the AA-12 missile on the left?
The advantage of grid fins in rocket’s is that they work really well under high speeds and require a much smaller surface area then a conventional planar fin, the result is a robust system that allows SpaceX to control the decent of its Rocket’s as they fall back to earth. SpaceX utilised grid fins for space flight when in February 2015 the falcon 9 successfully landed its first stage rocket with the help of grid fins. See Below picture showing the Falcon 9 grid fins.