Spatial extent of the initial (z ∼ 20) gas distribution that fuels the assembly of in situ (solid curves) and ex situ (dashed) stars by z = 0. We offer three different measurements: the median distance of tracers (blue), the 95^th percentile distance (orange), and the radius of the sphere whose volume equals that of the convex hull of the initial gas distribution (green). As expected, the collapse of gas into more massive halos takes place from initially larger scales.