Meridian is the resonance passageway for energy in life message. As long as the resonance frequency of the energy in the message is the same with that of the transmitter, message energy can pass through. Therefore, no tangible tunnel is needed and meridian is not found in dead body from anatomy. Energy measuring instruments, such as the thermograph, are used to measure the energy in the meridian, the changes of the meridian and display the existence of meridian itself. The carrier of life energy is far infrared (IR) electromagnetic wave. By showing the transmission of far IR electromagnetic wave, the passage way of energy in life message (meridian) is located. To prove the existence of meridian and its function, before and after the acupuncture, position emission tomography (PET) is used to display the condition of bio-molecule metabolism, receptor and neurotransmitter on molecule level, single-photon emission computed tomography (SPECT) is used to observe the mutual influence and change of blood in the Zang-Fu organ and meridian. A living person has life message and meridian, while a dead person does not have any life message and meridian.