Extracellular

This refers to anything occurring outside of a cell/cells. This could include the extracellular matrix- this is a complex network of many polysaccharides (e.g. cellulose) and proteins (e.g. collagen) secreted by cells in which the cells are embedded. It could also include extracellular signal molecules- these are any secreted or cell-surface biochemical signal that bind to cell surface receptors and regulates biochemical pathways within the cell.