According to Chinese medicine theory, acupuncture works primarily by promoting the free movement of energy, which acts to balance and harmonize the body. Western scientific research has shown that acupuncture causes the production of the morphine-like pain suppressing molecules in the body called endorphins. However, acupuncture is used for many other conditions besides pain. More recent research has provided explanations for how this works. These studies have shown that when an acupuncture needle is inserted into the body, specific regions of the brain are activated. This brain activation then allows regulation of other systems in the body primarily through the modulation of molecules such as neurotransmitters and hormones. Collectively scientific research has shown that acupuncture can modulate all the primary systems in the body including the nervous, endocrine and immune systems. Current research is aimed at understanding exactly how this happens, and the nature and specific usage of the various acupuncture points for different medical conditions.