Circumventing spatter Laser powder bed fusion is an additive manufacturing technique that laser-melts powder layer by layer to build a three-dimensional (3D) part. Khairallah et al. used experiments and a multiphysics model to determine the origin of the melt spatter and defect formation that degrade the properties of built parts (see the Perspective by Polonsky and Pollock). Informed modulation of laser power is important to avoid disturbing the powder bed and creating laser shadowing. This reduces pore formations and leads to more uniform properties of 3D-printed parts. Science , this issue p. 660 ; see also p. 583