The image above shows a piece of the sky in the constellation Fornax, and it's about 16 arcminutes across. By comparison, your pinkie's fingertip is about 60 arcminutes across and the moon is about 31 arcminutes across. Chandra says about 2,076 galaxies (and their supermassive black holes) are lurking in the photo, which they called "the deepest X-ray image ever obtained."
The dots reveal the locations of the supermassive black holes.
Astronomers can "see" these monsters because they round up stars, gas, and dust in a region called an accretion disk, which gets very hot and emits the X-rays. Low-energy X-rays are shown in red, medium-energy in green, and high-energy in blue.
These galaxies are between 11.9 and 12.9 billion light-years away from Earth — so distant it's like looking back in time.