The levels of organization in the body starts in a molecular level. In the case of the digestive system, some molecules that are important involve carbohydrates, proteins and fats. The molecules are organized into organelles and organelles are organized into cells, working together to build and make a cell work. Cells, then, will compose the tissues. In a digestive system, the tissues will then create the organs, such as the stomach, the liver and the intestine. Those are all organs composed of tissues. The organs, then, will work together and be organized into systems. In the case of the digestive system, all of the organs that are neede for digestion are connected and, together, create the digestive system. All of our body systems, organized, work together so our body can function as a whole.