The smallest mass standard sold until now had a nominal value of one milligram. In order to address emerging needs, the joint LNECNAM metrology laboratory decided to produce and calibrate micromass standards with nominal values down to 100 µg. These standards were developed, then tested through multiple comparisons. They have since been qualified and calibrated through a weighing design, repeatedly and over an extended period of time, so as to establish their stability with respect to oxidation and harmlessness of the handling and storage procedures associated with their use. After five successive calibrations no significant drift was found. Finally, in order to enhance this development, the laboratory obtained an extension of its accreditation to perform mass calibration allowing the extension of the lower limit of the scope of accreditation from 1 mg down to 100 µg.