Groups of different kinds of tissue working together form organs. An organ is defined as a group of tissues that work together to carry out a certain task.
A good example is the heart , a vital organ of the body. It is made up of three different kinds of tissue namely muscle tissue, nerve tissue and blood tissue. Its job is to pump blood throughout the body.
Organs are made of groups of tissues, tissues are made of groups of cells working together. A tissue is defined as a group of cells working together to carry out a certain job in the body. Examples of tissues include nerve tissue, skin tissue, bone and blood.