The private SpaceX company landed a spaceworthy rocket (or the first stage anyway) upright onto a pad at Cape Canaveral--just the way Rocky Jones, Tom Corbett and Buzz Corey of Space Patrol did on Saturday mornings in the 1950s, but which had never been done in the more than fifty years of actual space flight.
(Unless you count the smaller craft that did it recently, launched by another private company, Blue Origin.)
widely considered a landmark, for if rockets can be reused, it might well make using rockets, especially for space travel, a lot less expensive.
For what Rocky Jones and other rocket jockeys did routinely has been out of reach of actual rocketeers. When real manned spacecraft began "lifting off" (rather than "blasting off!") in the early 1960s, they left their booster stages behind to fall into the sea or remain in orbit, and astronauts huddled in the top capsule that returned attached to parachutes.
The best that was done after that were the Space Shuttles that landed like airplanes on a runway. Of course, the even more budget conscious Star Trek series solved the problem in 1966 by never landing the Enterprise, and beaming people down and back up.
Though science fiction got a lot right in the years before actual spaceflight--and in fact inspired a lot of what actually was done, like the design of spacesuits and the countdown--this was a key difference. If rocket ships just took off and landed (even if, like Flash Gordon, the ships belly-flopped rather than landing upright), they could be more plentiful.
If rockets were as reusable and cheap as airplanes, they might have had a greater impact on life on Earth, as well as making space travel more frequent and even ordinary. That's the kind of near future that Robert Heinlein saw, for instance, in his first 1950s science fiction novels for young readers, Rocketship Galileo. In a future that seemed a lot like the 1950s, rockets were routinely used to transport cargo, because they were faster than airplanes and reusable. In fact, it's an old cargo rocket that our young heroes refit for their pioneer voyage to the moon.
Arthur C. Clarke once said that the only thing that surprised him about manned space exploration was that it stopped. The gigantic expense was a big reason it did. The head of SpaceX is Elon Musk, who despite his name is believed not to be an alien himself, but he's very focused on manned space exploration, especially to Mars.
It's still a pricey proposition, with lots of technical problems that may never be licked, especially involving how to keep humans alive for the voyage and on Mars. But the reusable rocket is a step in that direction. Maybe a big step.