Retinas were sectioned en face to isolate the vascular layer and stained with fluorescent-labeled isolectin. Tip cells (arrowhead) were identified by their position at the distal edge of the vasculature and by the presence of filopodia in P1 or P2 retinas. (A) Stalk cells (arrows) and adjacent nonvascular retina tissue (*) were also harvested. (B) Burn marks indicate where tip cells have been removed by LCM (arrowheads) from P2 retina. Circle represents the optic nerve head region.