Working out has a positive effect on health but just how physiologically complex is exercise? Studies are now showing how movement demands coordination between different body systems. It seems that fat cells communicate with muscle cells who in turn communicate with the brain and finally the liver. The Garvan Institute of Medical Research in Sidney, Australia has begun to look at what is known as vesicles within the cells. These are tiny microscopic globules, similar to little boats, that are responsible for transporting waste material out of the cells and into the blood to be excreted out of the body. It is now known they are also an important messenger carrier. After extracting blood samples from men before and while performing intense exercise they noted an increase in these tiny vesicles. Upon tracking these vesicles with fluorescent markers after injecting them into mice, it was noted that these vesicles travelled directly to the liver instructing it to rev up energy production in order to accommodate for the increase in energy expenditure. The study reveals the complexity of what happens in the blood during exercise.This is how the liver is aware of what is happening and how it is able to transfer that information to cells farthest away from itself that may also need energy. As a result, scientists are able to get clearer insight into how metabolism actually works.