Researchers have taken an important step towards 3D printing of high-strength metals. Despite the huge growth of 3D printing in recent years, the way metal grains are printed and incorporated can lead to microstructures with large columnar grains and periodic cracks. John Martin of HRL Laboratories and the University of California and colleagues have shown that adding nanoparticles to the metallic powders used as the “printer ink” results in crack-free and regularly grained printed materials with strengths comparable to wrought materials. More than 5500 alloys in use today could potentially benefit from the technique.