Heterogeneous catalysis plays a leading role in the chemical industry.Creating heterogeneous catalysts with minimal use of metals but well-defined catalytic sites is highly desired for developing cost-effective and green chemical processes.With single metal atoms dispersed on supports,single-atom catalysts are featured in their optimized usage of metal and also the similar chemical environments of metal sites.It has been long believed that the single-atom catalysts should not be stable enough to be prepared via conventional catalyst-preparation techniques.However,in 2011,Tao Zhangs group in Dalian Institute of Chemical Physics,cooperating withJun Li from Tsinghua University andJingyue Liu from Arizona State University,successfully demonstrated the feasibility to fabricate stable and efficient single-atom Pt catalysts using a simple co-precipitation method.The research also presented a systematic methodology to investigate single-atom catalysts using advanced characterization techniques.During the past several years,the work has greatly stimulated the rapid development of the field.There are now numerous studies demonstrating that single-atom catalysts serve as an excellent catalyst system to bridge homogeneous catalysts with well-defined molecular structures and heterogeneous catalysts with structural complexity.With more and more contributions to this rapidly growing field,single-atom catalysts have been emerging as next-generation heterogeneous catalysts for various applications.