Huge 3D Printing Breakthrough! Caltech is printing metal atom by atom. A hydrogel scaffold soaked in metal salts becomes the blueprint, the gel burns away, and oxygen is stripped in a hydrogen-rich chamber, leaving alloys crafted with surgical precision. They can change metal ratios on the fly. Flip from a copper-heavy mix to a Cu12Ni88 alloy nearly four times stronger, without altering shape or tooling. Every property, from strength to density, is now designed, not guessed. This is metallurgy reinvented. Also a game changer for Aerospace applications.