The basic tissues like epithelial tissue, connective tissue, muscle tissue and neural tissues organise to form organs which in turn associate form organ systems in the multi cellular organisms. Such an organisation is essential for more efficient and coordinated activities of millions of cells constituting an organism. Each organ in our body is made up of one or more type of tissues. For example, our heart consists of all the four types of tissues. i.e., epithelial , connective, muscular and neural .