Your body system’s internal balance. In order for the cells in your body to function, the environment they live in must be carefully controlled – just the right amount of a huge number of different substances like water, oxygen, glucose, and a ton of other things must be kept in balance at all times or your cells deteriorate, mutate or die. Your body system is constantly at work balancing this myriad of substances such that precisely the right proportions of everything are constantly in your cell’s surroundings. Drink a lot of water, your body removes the excess from your blood. Consume a candy bar, your pancreas and liver work to process the excess sugar out of your system. Do a lot of physical exercise and your body produces sweat to keep your temperature within a very tight range.