World’s most sensitive scales weigh a zeptogram

The world’s most sensitive scales can now detect a cluster of xenon atoms a billion, trillion times lighter than a gram. A zeptogram (10^-21)g) is roughly the mass of a single protein molecule and its detection has set a new record.
The feat opens up the prospect of future devices that could identify single molecules by weight, providing a sensor of extreme sensitivity that would be valuable in medical and environmental testing.
The key to the scales is a small blade that vibrates in a magnetic field, generating a voltage in an attached wire. When atoms or molecules are placed on its surface, they weigh it down, lower the vibration frequency and change the voltage.