The growing demands for electric automotive and regenerative energy storage applications, and the increasing caring for climate change and pollution, drive the search for high-performance electrochemical power sources that are also safe to operate, economically viable and environmentally friendly. Compared to LIBs and NIBs, very little is known about the electrochemical storage mechanism of KIBs. Here in operando studies including in-situ Raman and in-situ XRD characterizations, ex-situ XPS analysis and ab initio calculations are carried out for correlating the real-time electrochemical K⁺ intercalation process with structure/component evolution. Our results reveal three distinct intercalation stages are involved for K⁺ storage in few-layered graphene, corresponding to the formation of different GIC stages (e.g., KC₃₆, KC₂₄ and KC₈). The K⁺ diffusion coefficients are found to be GIC stage dependent based on GITT and EIS results, corroborating the diversity in K⁺ intercalation pathways. The establishment of clear property-structure relations in this work promotes better understanding of the K⁺ storage mechanism in graphite and opens up a new exciting direction for designing new materials for K-ion Batteries.