The start of the modern era of NNPs for chemical reactions can probably be assigned to the emergence of fully dimensional PIP-NNs developed by Jiang and Guo that started a burst of explorations of RMLPs on small systems . Starting from simple three-atom systems H + H 2 and Cl + H 2 in 2013 , the usage of PIP-NN was further expanded to larger reactive systems , molecule-surface interactions such as hydrogen on a Cu/P t surface and to the fitting of coupled diabatic potential energy matrices . In addition, the Raff , Le , Li , Zhang and other groups also contributed to development and building of RMLP for small reactive systems and further applications in spectroscopy prediction as well as reactive MD simulations. Extensive descriptions of these efforts have been made by previous reviews , so we will not go into details in this paper.