We are grateful to Weiyao Ke, Guang-You Qin, Yasuki Tachibana and Daniel Pablos for helpful discussions. We thank Wei Chen, Yayun He, Tan Luo and Yuanyuan Zhang for their collaboration on many results presented in this review. This work is supported by the Director, Office of Energy Research, Office of High Energy and Nuclear Physics, Division of Nuclear Physics, of the US Department of Energy under Grant Nos. DE-SC0013460 and DE-AC02-05CH11231, the National Science Foundation (NSF) under Grant Nos. ACI-1550300, ACI-1550228 and OAC-2004571 within the frame-work of the JETSCAPE Collaboration, and the National Natural Science Foundation of China (NSFC) under Grant Nos. 11935007, 11221504 and 11890714.