As computing power continues to improve, the horizontal grid resolution of numerical weather prediction models has reached the kilometer-to-sub-kilometer scale. This grid scale is comparable to the characteristic turbulent scales in the convective boundary layer, allowing the numerical models to resolve the organized convective structures. The assumptions of traditional one-dimensional boundary layer parameterization schemes (suitable for horizontal resolutions of several kilometers or coarser) and large eddy simulation three-dimensional turbulent closure schemes (suitable for horizontal resolutions below several tens of meters) do not hold at this scale, which is referred to as the gray zone. This study discusses the applicability and limitations of traditional parameterization methods and introduces the gray zone of the convective boundary layer from three perspectives: theory, methodological approaches, and impact. It summarizes the characteristics of the simulation methods at the CBL gray zone scale developed over the past two decades and explores the impact of the boundary layer process simulation at this scale on other physical processes (e.g., shallow/deep convection) in numerical models. Further, we anticipate future research directions and approaches.