Schematic diagram showing key molecular regulators of EC tubulogenesis and pericyte recruitment to EC tubes which control capillary network formation and maturation. Dynamic and polarized EC-pericyte interactions within vascular guidance tunnels results in abluminal vascular basement membrane matrix assembly. EC tubulogenesis is driven by growth factor-dependent signals secondary to a special combination of five growth factors (“Factors”) which are SCF, IL-3, SDF-1α, FGF-2 and Insulin. VEGF can prime ECs in an upstream step to facilitate their responsiveness to the “Factors”. These “Factors” stimulate an integrin-, MT1-MMP-, and Rho GTPase-dependent signaling cascade which controls the development of EC tube networks and vascular guidance tunnels in 3D matrices. These networks produce PDGF-BB and HB-EGF to induce recruitment and proliferation of pericytes and together ECs and pericytes co-assemble within tunnel spaces to co-contribute and deposit the vascular basement membrane along the abluminal EC tube surface in between the two cell types.