Humankind has remote-controlled plenty of objects in space before, but up until this week, no space-to-ground control — a vital component in mankind's future invasion of other planets — had happened.
The demonstration of remote control was conducted by ISS astronaut Terry Virts and the ESA this week, and was pretty basic: Virts moved a joystick on the ISS, which moved an identical joystick on the ground in the Netherlands. The system is meant to let astronauts interact with objects from thousands of miles away — for example, operating a rover on Mars whilst in orbit around the Red Planet.
From the ISS, the signal from the joystick had to travel to another communications satellite, from there to Houston, and then across the Atlantic to the Netherlands. All in, the round trip — from the ISS to Earth, and back — took 0.8 seconds. 800 milliseconds would be a pretty bad ping if you're trying to play Counter-Strike, but for interplanetary remote control, it ain't bad.
More importantly, it's a lot better than the 12 minutes it takes for commands to travel from Earth to rovers on Mars. The European Space Agency envisages an intermediate step in sending astronauts to Mars: before a round-trip mission can land humans, and then return them safely, we should put astronauts in orbit, and have them explore the planet below using robots. Space-to-ground remote control would be a vital part of that. Moving a joystick is a long shot from driving a multi-billion-dollar rover around all those Martians, but it's an impressive baby step nonetheless.