A new type of microwave laser, a maser, has been built by scientists in the UK using diamond. The maser, microwave amplification by stimulated emission of radiation, was invented in 1954 but until now they could only be operated at close to absolute zero. Research in this area has now warmed up. A team from Imperial College London and University College London has developed a maser that operates in continuous mode at room temperature. The new devices follows on from burst-mode maser developed in 2012 at Imperial College that used pentacene. The new device uses a synthetic diamond with introduced vacancies filled with nitrogen atoms where normally there would be carbon. The modified diamond is held in a sapphire ring and bathed with green laser light, this leads to generation of coherent microwaves. Such a relatively simple setup could open up medical imaging and a new type of security scanning as well as new avenues of materials science research.