The lateral incorporation of graphene and hexagonal boron nitride (h-BN) onto a substrate surface creates in-plane h-BN/graphene heterostructures,which have promising applications in novel two-dimensional electronic and photcelectronic devices.The quality of h-BN/graphene domain boundaries depends on their orientation,which is crucial for device performances.Here,the heteroepitaxial growth of graphene along the edges of h-BN domains on Ni(111) surfaces as well as the growth dynamics of h-BN using chemical vapor deposition (CVD) are in situ investigated by surface imaging measurements.The nucleating seed effect of h-BN has been revealed,which contributes to the single orientation of heterostructures with epitaxial stitching.Further,the growth of h-BN prior to that of graphene is essential to obtain high-quality in-plane h-BN/graphene heterostructures on Ni(111).The “compact to fractal” shape transition of h-BN domains appears with the increasing surface concentration of the growth blocks,suggesting that the dynamic growth mechanism follows diffusion-limited aggregation (DLA) but not reaction-limited aggregation (RLA).Our results provide insights into the synthesis of well-defined h-BN/graphene heterostructures and deep understanding of the growth dynamics of h-BN on metal surfaces.