Glycol methacrylate (JB-4) sections of eyes at 5.5 (A–B), 7 (C–D) and 12 WG (E–F) showing the blood vessels in vitreous and the hyaloid artery. The hyaloid artery at 5.5 WG had not penetrated the vitreous cavity but was present in the optic stalk (arrow in A & B). Near the lens vesicle, blood island-like structures were formed in vitreous cavity (paired arrows in A). The hyaloid artery at 7 WG had invaded the vitreous and contained packed erythroblasts (arrow in C & D). Blood vessels were present near the lens in the vitreous and on the surface of the lens (paired arrows in C). The hyaloid artery was fully formed by 12 WG and had several major branches near the posterior surface of the lens (arrow in E). The outer wall of the hyaloid artery had smooth muscle cells (arrowheads in F). (A–C hematoxylin & eosin stain, D Wrights-Giemsa stain, E & F Periodic acid-Schiff and hematoxylin stain, Scale bars = 100 μm in A,C & E, 20 μm in B,D & F) (Fig. 1 from McLeod et al., Invest. Ophthalmol. Vis. Sci. 53:7918, 2012, with permission).