IC 2944 is an emission nebula, 6500 light years away from us in the constellation of Centaurus. You can see dark clouds in front of the glowing hydrogen gas. These dark clouds are the main ingredients of new stars which are currently being formed inside the clouds. The clouds have typical masses of about 2 to 50 solar masses and their diameters are more or less one light year. They are also called Bok globules since in the 1940s the astronomer Bart Bok already suspected them to be possible regions of star formation. The particular ones you can see on this image are nicknamed Thackeray Globules. These dark clouds mainly consist of molecular hydrogen (H2), helium, carbon monoxide and cosmic dust. The dust within them is the main ingredient for planets which form around stars.
If interested, read more about: Emission nebula - Molecular Clouds and Dark Nebulae