This is a Star forming region in the constellation Sagittarius. It is one of the only two star-forming nebulae which can be seen by the earthbound sky-grazers with unaided eyes from mid-northern latitudes. In the time-exposure photographs, this region looks beautifully coloured (an emission nebula emits light in different colors/wavelengths), but it appears gray to human eye when seen from here due to our unfortunately poor color sensitivity at low light levels.
The region captured here is wide – even if you travel at the speed of light, you will take three years to go from from left hand side of the picture till the right edge.
Here is a beautiful ‘Let-us-zoom-into-the-lagoon’ one-minute Video from Hubble: