Multi-cellular organisms, such as plants and animals, have a higher degree of specialization where the cells work together and function to create a living organism.
Example: a human – starts as a single cell. Then organize themselves into three groups called germ layers. One layer will form the skin and nerves, Another layer becomes the lining of the digestive tract. The third layer produces all other body parts. http://www.youtube.com/watch?v=qEHQbjido9I