Scanning electron micrograph shows a clump of Staphylococcus epidermidis bacteria in the extracellular matrix, which connects cells and tissue. Staphylococcus epidermidis is one of 33 known species belonging to the genus Staphylococcus. It is part of human skin flora (commensal), and consequently part of human flora. It can also be found in the mucous membranes and in animals. Due to contamination, it is probably the most common species found in laboratory tests. The extracellular matrix (ECM) is the extracellular part of animal tissue that usually provides structural support to the animal cells in addition to performing various other important functions. The extracellular matrix is the defining feature of connective tissue in animals.