These red dots represent some of the earliest galaxies known to astronomy. Located ten billion light-years away, they're only a few billion years older than the Big Bang. Their presence explains why we're now surrounded by massive elliptical galaxies.
A basic fact of the universe is that space is a dark, black expanse that's only broken up by the lights of stars and galaxies. But that wasn't always the case — space was once a dense, opaque fog.