Collapse and disk build-up of the gas parcels in the standard model. Each set of three panels shows the collapse at 0.05,0.25,0.5, and 0.75 t_acc over three length scales. The left panel shows the largest scale, the envelope scale, and the right panel shows the length scale relevant to the disk. The colour of each point denotes the initial radius range from which the parcel originates. Dark brown denotes an initial radius smaller than 1000 AU, orange a radius between 1000 and 2000 AU, and so on. The embedded disk builds up from gas that successively falls from higher heights as well as from the viscous spreading of the disk itself. For reference, the black line shows an estimate of the location of the rarefaction wave defined by x = 1.