Hint: As we know, the group of cells which works together as a unit is called tissue. Tissues are of two types: simple tissue and complex tissue. The simple tissue consists of only one type of cells while the complex tissue consists of more than one type of cells.
Complete answer: In this question, we have asked about the complex tissue. As we already mentioned, complex tissue is a group of more than one type of cell which works together as a unit. - The main function of complex tissue in plants is transportation of organic material, water, and minerals. - They are also known as conducting or vascular tissue. Examples of complex tissue are: xylem and phloem. - As we know xylem consists of tracheary elements, xylem parenchyma cells, and xylem fiber cells and the phloem consists of sieve tubes, companion cells, phloem fibers, and phloem parenchyma cells. - Xylem transport water and minerals dissolve in it and it also transports some molecules like hormones. - Prepared food or organic substances are mainly transported by phloem from leaves to other parts of the plant.
In animals, an example of complex tissue is blood. In blood different cells are found: red blood cells, white blood cells and platelets. All these different kinds of blood cells function together for carrying the oxygen, water and nutrients to all parts of the body.
Note: If the tissues are composed of only one type of cells i.e all cells are functionally and structurally similar, then they are called simple tissue. Examples of simple tissue are parenchyma, collenchyma and sclerenchyma.