Superconducting nanowire single-photon detectors (SNSPDs) are significantly better at photon detection efficiency (DE) compared to their semiconducting counterparts, and have enabled many breakthrough applications in quantum information technologies. A team headed by Prof. Lixing You from Shanghai Institute of Microsystem and Information Technology (SIMIT), Chinese Academy of Sciences (CAS) have demonstrated the fabrication and operation of an NbN-SNSPD with system detection efficiency over 90 percent at 2.1 K at a wavelength of 1550 nm, which paves the way for practical application of SNSPD.