To our best knowledge, the quark is an elementary particle and a fundamental constituent of matter. Top-quark is the giant in his family (its mass is rough equal to a gold atom). It once existed copiously in our Universe long time ago, according to the "big bang" theory, but it is no longer around us as it flares briefly and then burn out into lighter particles. Today the top-quark can be seen only in the laboratory through high energy collisions. The lifetime of top-quark is only about 10^-25 second. It is impossible to observe such an ephemerality particle directly or to measure its detailed properties. In fact one has to rely on the top-quark decay products to confirm the top-quark event and to reconstruct its kinematics. Unfortunately, the top-quark pair is usually produced in associate with those invisible dark matter candidates in a lot of new physics models. One then has to confront with the incapability of reconstructing top-quark event. Dr. Qing-Hong Cao and his collaborators invented a novel method of measuring the top-quark polarization in the top-quark pair plus missing energy events. In the method the top-quark reconstruction is no longer needed. The method can improve greatly the current experimental search for new physics, as quoted from the referee, 'improved methods for measurement of top quark polarization are crucial for the LHC physics since so many top quarks are being produced as expected and might also be via new physics since the top quark is so massive. The top quark is also possibly uniquely related to unknown fundamental electroweak physics.' The work is published in the journal of Physical Review Letters [Phys. Rev. Lett. 109, 152004 (20120].