Lactate the byproduct of glycolysis has long been considered as a waste metabolite. The discovery of Warburg effect in cancer cells brought our attention back to lactate and inspired us to uncover the crucial roles of lactate in serving as fuel acting as a signal molecule promoting angiogenesis and suppressing immune cells. However the mechanism regarding how lactate regulates these biological processes remains elusive. As we known thousands of metabolites will be produced during life activities. They are not only the products catalyzed by proteins enzymes but also can in turn affect the function of proteins through covalent modification. In 2019 and 2020 lactate was reported to be the substrate of lactylation by two independent studies and this novel post-translational modification revealed another layer of molecular mechanism by which lactate regulates cellular activities. In this review we briefly describe the discovery of lactylation and we summarize the recent advances with respect to the potential 􀆵writer and 􀆵eraser of lactylation the profiling of protein lactylation in a variety of organisms and the regulatory roles of lactylation in diverse physiological and pathological processes. Key questions and potential implications for future studies on lactylation are also discussed.