This new scale can detect mass differences of an attogram (10^-18 grams)
"The nanoelectromechanical device used by Craighead and colleagues consists of an oscillating cantilever made from a small wafer of silicon 4 microns long and 500 nm wide. When a small particle is absorbed onto the wafer, it alters the frequency at which the wafer vibrates. The team was able to monitor this change by measuring laser light reflected off the wafer, which then allowed the mass of the particle to be calculated."
