Diamonds aren't just glittery, sparkly gems for jewelry. The smallest ones, only a few nanometers wide, are also crucial for drug delivery, sensors and quantum computer processors. Producing diamond nanoparticles that are consistently sized is important to the success of these technologies. Now, scientists report a method to grow ultra-uniform nanodiamonds without the need for explosives. The technique also could be used to add beneficial single-atom defects in otherwise perfect crystals.