 3D printing technology called selective laser melting, SLM, is gaining popularity for its ability to produce complex metal components with customized production benefits. A study shows that additively manufactured 304L austenitic stainless steel with low stacking fault energy has superior fatigue resistance than conventional counterparts due to its unique heterogeneous microstructure, despite containing high porosity. The study reveals that the cellular substructure plays a crucial role in regulating dislocation motion during cyclic deformation, resulting in intergranular fatigue cracking along HAGBs rather than twin boundaries. This article was authored by Hongzhuang Zhong, Mengdao Shu, Panit Kumar, and others.