INTRODUCTION: Photonics refers to the technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. Photonic technology in the meridian and acupoints research has shown the unique advantages, by which the microcosmic material basis and macroscopic phenomena research can be integrated to interpret the occurrence of propagated sensation along meridian (PSM) and its underlying mechanism. This study seeks to investigate light and heat sensing action along meridian.METHODS: From the modern research of meridian point of view, PSM is the break point to research the essentiality of meridian. The bio-photonic feature of meridian is the most promising research direction to investigate the PSM phenomena for its contribution to prove the existence of meridian objectively and spontaneously. Therefore, the bio-photonic features of meridian under physiological, pathological, therapeutic, and mechanical conditions were analyzed. Firstly, the four aspects of light sensing action were discussed, i.e. light sensing effect along meridian, blocking effect, laser induced effect and underlying mechanism of light sensing action along meridian. Secondly, the four items of heat sensing action were discussed as well, i.e. thermo-effects, heat perception ability, laser induced heat effect, underlying mechanism on heat sensing effect along meridian.RESULTS: The authors point out that photonic technology, e.g. ultra-weak luminescence, photonic imaging, infrared imaging and infrared spectrum analysis, biological photons detection and laser Doppler application, can achieve purposes of in vivo, dynamic, multiple comparable studies. Thereby, the effect of light and heat sensing along meridian can be detected and illustrated by the use of natural science. The effect of light sensing and heat sensing along meridians with the help of advantages of photonics is expected to interpret and quantify the meridian doctrine, to provide an important experimental basis for meridians and acupoint properties of light and heat, to find a kind of non-invasive diagnostic technique, and to promote the integration and development of meridians and modern medicine.CONCLUSION: Light and heat information can be investigated to analyze the relationship between zang-fu organs and meridians, and the functional characteristics of the meridian. Hence, the effect of light and heat sensing along meridian is the break point of the research of photonics in meridian, which is beneficial to further study the meridian optics
