Yes, we've found quite a lot. Aliens aren't entirely uncommon on Earth to begin with. But we've found at least 4 entire extraterrestrial empires, the Skrulls, Shi'ar, and Kree being the most prolific. I understand from Pepper that you've encountered the Chi'tauri as well.

[An apologetic look. The Chi'tauri were bad news, not Skrull bad, but bad.]

The bigger discoveries? The Negative Zone, a universe outside our own. Think...if reality divided by zero. Then there's the Titans and Celestials, mad star gods. And Galactus...

[She trails off there. He's...not her favorite subject even if Reed's technically his friend]