A doctor does not work alone. He or she works with other doctors, nurses and medical staff to make people healthy. A builder does not work alone. There are other builders who help do the same job. Likewise, most cells do not work alone. They work with other similar cells to form what is called a tissue.
A tissue is a group of similar cells that all work together on the same job. For example, tissues in your lungs are made up of millions of similar cells working together to transport oxygen to the blood. Blood itself is a liquid tissue that transports oxygen, food and waste throughout the body.
Different types of tissues come together to form organs. For example, the heart is an organ made up of muscle tissue, blood tissue, and nerve tissue. An organ has an important job that keeps the living thing alive.
Like animals, plants also have organs. Common plant organs are leaves, stems and roots.
