Only one thought comes to mind when I look at this, and that thought is 'jaw-dropping.' This region, which lurks approximately 4,000 light-years from Earth in the constellation of Sagittarius, has many areas of interest, starting with Simeis 188—the cloud that houses the nebular complex, and all of the stars within its walls.
The grayish-black arc that sweeps across the top and to the left of the frame is NGC 6559. The regions that bask in vivid red signal the existence of emission nebulae, which are common fixtures throughout the universe, being that they are tied to star formation. Then we venture into the accompanying blue hues—reflection nebulae. They form when light from embedded stars encounters dense concentrations of dust, scattering more efficiently toward the blue end of the electromagnetic spectrum. Pretty much every other type of nebula is represented here as well, including dark nebulae and absorption nebulae.