There are different kinds of cells. For example, muscle cells are long, and they have specialized in contracting and relaxing. 

A nerve cell can sense things and transmit information. Blood cells are small cells that transport materials through the circulatory system. Skin cells are durable and help to protect your body from the outside world.

Usually, similar cells are located next to each other. When similar cells are joined together, they create tissues. For example, your muscles are made of muscle tissue, which in turn consists of muscle cells.

Together, different tissues form organs. Organs are structures that fulfill specific functions in the body. For example, the heart is an organ that consists of muscle tissue, supporting tissue and nerve tissue.