Acupuncture is traditionally based on the theory of meridians and collaterals. According to this theory, energy and blood circulate in the body through a system of channels called meridians. These meridians connect internal organs with external organs or tissues. By stimulating certain points on these meridians, the flow of energy and blood can be controlled. The stimulated points are called acupuncture points, or acupoints. Modern medical acupuncture is based on Traditional Chinese Acupuncture. The main difference is the science behind where the needles are placed. Medical acupuncture treatments usually follow physical pressure points in the body.