SpaceX founder Elon Musk gave Stephen Colbert and millions of Americans a window into the future Wednesday on The Late Show.

Though Musk's ambitions for interplanetary travel and Tesla's electric car technology led Colbert to compare him to Iron Man's fictional superhero Tony Stark, Musk says he's merely trying to do "useful things," not save the world.  

"The most important thing we need to solve this century is sustainable energy," Musk said.

So where does Musk see technology taking the human race? Here are three predictions he made on Wednesday's show.

1. Mars will be habitable for humans.

Musk: [Mars] is very inhospitable. It's is a fixer-upper of a planet. First, you're going to have to live in transparent domes, but eventually you could transform Mars into an Earth-like planet.

Colbert: How?

Musk: You'd make it warm enough. The fast way is to drop thermonuclear weapons on the poles. The slow way would be to release greenhouse gasses like we're doing on Earth.

2. Multiplanetary life can be affordable.

Musk: The key to getting life to be multiplanetary is to have reusable rockets. If you throw the rockets away every time, it's crazy expensive, but if you can reuse the rockets, it could be comparable to air flight in its costs.

3. Humans will soon fly in SpaceX's reusable rockets.

After showing footage of SpaceX's Falcon 9 crashing and exploding while attempting to land at sea, Colbert asked Musk when he thought reusable rockets would be able to takeoff and land safely.

Musk: In terms of when it will be safe enough for people, it will be two to three years. In approximately two years, we'll be transporting NASA astronauts to the space station.

Colbert will interview Uber co-founder Travis Kalanick tonight at 11:35 pm ET.