Completion of genome sequences for many organisms allows a reasonably complete 
definition of the complement of extracellular matrix (ECM) proteins. In mammals 
this "core matrisome" comprises ∼300 proteins. In addition there are large 
numbers of ECM-modifying enzymes, ECM-binding growth factors, and other 
ECM-associated proteins. These different categories of ECM and ECM-associated 
proteins cooperate to assemble and remodel extracellular matrices and bind to 
cells through ECM receptors. Together with receptors for ECM-bound growth 
factors, they provide multiple inputs into cells to control survival, 
proliferation, differentiation, shape, polarity, and motility of cells. The 
evolution of ECM proteins was key in the transition to multicellularity, the 
arrangement of cells into tissue layers, and the elaboration of novel structures 
during vertebrate evolution. This key role of ECM is reflected in the diversity 
of ECM proteins and the modular domain structures of ECM proteins both allow 
their multiple interactions and, during evolution, development of novel protein 
architectures.