TISSUE
Tissue in biology is an assembly of cells, which are integrated by common origin, structure and the functions, which they perform. All cells in tissues are in contact with a complicated network of extracellular macromolecules, which is called extracellular matrix. Extracellular matrix participates in maintenance of integrity of tissues. It forms a well-ordered spatial frame, inside of which cells can migrate and interact with one another. The cells, which contact neighbouring cells directly, are often joined to them not only by the extracellular matrix, but also by specialized regions of plasmamembrane. Such regions are called intercellular unions.
Animal tissues are: epithelium, all kinds of connective tissues, muscular and nervous tissues. Plant tissues: meristem, parenchyma tissue, protecting and conductive tissues. Various tissues group together into functional units of higher order named organs.