Anirudha V. Sumant considers how diamond thin films are making a comeback after slowing down in the late 1990s due to technological hurdles. Researchers at Argonne National Laboratory invented ultrananocrystalline diamond (UNCD) in 1998, which has grain sizes of 2-5 nm, low roughness, and high hardness and conductivity. UNCD was found to have applications in areas like electrodes, sensors, and coatings. Recent research has shown that UNCD can be deposited at 400°C, allowing integration with semiconductor materials, and its smooth and conductive properties make it suitable for electronic devices. The technology of CVD diamond films has advanced to the point that commercial applications are emerging and the "diamond age