Cells in animal tissues are in contact with a structured set of well-defined proteins that constitute the extracellular matrix. Among these proteins, collagens are ubiquitous in distribution, whereas laminins are found only in basement membranes. In addition to their structural role, collagens and laminins convey messages to cells. A discussion is presented of the structure and diversity of collagens (about 20 types) and laminins (about 12 types). The nature of the cell receptors involved in message delivery (integrins and non-integrins) and the mechanisms possibly responsible for signal transduction are reviewed.