These figures show some results of 3D simulations of a collapsing gas cloud. The rows are different simulations, and the columns are different length scales, zooming in towards the right.
The figure below shows slices through the simulation box, centered on the densest object and looking at the x-y plane. The first and third column show the density field, overlaid with streamlines that indicate the velocity in the plane (so you can see gas moving towards the central object), where the thickness of the line is a measure for how fast the gas is moving. The second and fourth column show the gas temperature, using a different colormap more intuitive for heat maps.