Cellular responses to extracellular matrix

When the first experimental systems showing a biological effect of extracellular matrix on cells were presented about 20 years ago, for example, the stimulation of myoblast differentiation in culture by collagen [1], there was apparently no need for an exogenous matrix (ECM) control of cell differentiation—everything seemed to be determined by the genes, regulating all cellular events. For many years there was general scepticism about a specific role for the ECM in cell development and differentiation. How could such large macromolecules, many of which hadn't even been structurally characterized, exert specific effects on cells, and how would cells be able to recognize matrix molecules