In recent years, metal 3D printing, also known as additive manufacturing, has attracted considerable interest. This is largely due to its capability to directly produce components with intricate geometries and create distinctive microstructures. Among the various microstructures, cellular subgrain structures with a honeycomb-like appearance are especially remarkable. These differ significantly from the subgrain structures produced through traditional thermomechanical processing of metals. Despite the small misorientation (at the submicron level) between solidification cells and dislocation cells, these structures exert a substantial impact on the mechanical properties of the material. While these unconventional subgrain structures are commonly found in 3D-printed metals, the mechanism behind their formation has long remained a mystery. Recently, Assistant Professor Yang Guanghui and Professor Ma En from the Materials Innovation Center (CAID) at Xi'an Jiaotong University carried out a systematic investigation into this issue. By conducting thermodynamic and kinetic analyses, along with experimental characterization and numerical simulations, they have thoroughly uncovered the evolutionary pathway of cellular structures in 3D-printed metals and put forward a mechanistic framework for the formation of dislocation cells. Their relevant findings have been published in Materials Today, a prestigious journal in the field of materials science.