New Scientist is carrying this article summarizing the development of a new type of scale capable of measuring "zeptograms" (10^-21g). It's done using a vibrating blade of silicon carbide only 100 nanometers long.

The device already has potential uses in biomedical and environmental research. If researchers can make it even more sensitive, the device has the potential to diagnose diseases very early by identifying single marker molecules in a drop of blood.