The extracellular matrix (ECM) is composed of a variety of proteins including collagen, elastin, laminin, fibronectin, vitronectin, glycoproteins, and proteoglycans. Structurally, these proteins provide a mechanically dynamic and adaptable scaffold that is involved in processes including cell growth, differentiation, migration and contraction and remodeling. In consideration of the vasculature, we have demonstrated that the ECM can also present vasoactive signals to cells of the vascular wall that through outside-in mechanisms that convey soluble or mechanical signals to both vascular smooth muscle and endothelial cells. As examples, we and others have shown ECM fragments containing the Arginine-Lysine-Aspartic acid (RGD) sequence are vasoactive and can reduce vascular tone producing arteriolar dilatation as well as inhibit the vascular myogenic response to step increases in intravascular pressure. This evidence has led to hypotheses that integrins may act as injury receptors for soluble RGD containing fragments of ECM proteins that might present during vascular or tissue injury. Additionally, the integrins are thought to act as receptors that can convey mechanical signals from the ECM to the cell. Mechanistically integrins interact with a number of signaling pathways including ion channels important for vascular function. Fibronectin binding through cell surface integrins modulates the open probability of smooth muscle cell ion channels (voltage-gated Ca2+ channels and large conductance Ca2+-activated K+ channels) and can induce local cellular contractions at the level of a single focal adhesion. Despite our knowledge of the ECM in vasomotor control and vascular cell signaling, relatively little is known of the complexities of the in situ arrangement between specific ECM proteins and arteriolar smooth muscle cells. Evidence now exists to demonstrate that VSMC are rapidly adaptable in the sense of being able to adjust their position within the vascular wall during periods of prolonged vasoconstriction. This has been viewed as a form of acute remodeling and appears to involve alterations of the VSMC cytoskeleton as well as cell-ECM relationships. Given these examples, it is becoming increasingly clear that understanding the structural arrangement of the vessel wall ECM, particularly at the microvascular level, is vital for determining how local mechanical forces are transmitted, sensed and responded to and how vessels are able to interact with the ECM to alter vessel diameter. Recent studies in our laboratories have used three-dimensional confocal/multiphoton microscopy as a means to resolve structural details related to ECM protein distribution within the arteriolar wall. Our studies of elastin have revealed an elaborate network of organized fibers that course through the vascular wall. Functional studies of the elastin network demonstrate that it constrains arterioles longitudinally and when it is selectively compromised there is a resulting lengthening of the vessel. Collectively, knowledge of the role of the ECM in vascular control and the three-dimensional architecture of the extracellular matrix components within the vessel wall will help provide important new insights into our understanding of the structure-function relationships that exists in small arteries. Support to GAM NIH1P01HL095486.