Your body is made up of millions of cells. Mammals and plants are multicellular which means they have many cells. Each type of cell carries out a different function.
Differentiation This is the development of a young, unspecialised cell into a mature specialised cell. This enables cells to carry out a particular function.
Cells that are similar in shape and have a common function are often collected together and attached to each other. They form a tissue. A tissue is a collection of DIFFERENTIATED CELLS which are specialised for a particular function within the organism.
An example of a tissue. We know that a tissue is a group of cells with a similar structure. So, if we look at skeletal muscle, this is a TISSUE made up from skeletal muscle cells.
What is an ORGAN? Different tissues are grouped together to make an ORGAN. An organ contains several different tissues, all of which contribute to its overall function. An example of an organ is the pancreas. Organs work in groups called organ systems, eg, respiratory system.