Imagine you have two eyes, one on the left and one on the right. When you look at something with both eyes open, you can see it in 3D because your brain combines the pictures from both eyes.
Scientists want to do something similar in space - they want to use two telescopes to look at stars and other things in space. But since the telescopes are so far apart, they need to use some special tricks to make sure they're looking at the same thing.
They use something called "interferometry" - this means they combine the pictures from both telescopes to make one really detailed picture. It's kind of like taking a bunch of photos and putting them together to make a big panorama.
This helps scientists learn more about how stars and planets form, and what's inside them. The Space Interferometry Mission is a special mission that was planned to do this in space, but it hasn't happened yet.