Sensitive scale can measure a single zeptogram

"I think it's a fairly big step," says Kamil Ekinci now at Boston University in Massachusetts, who was Roukes' student when he did the attogram work. "It's the first time we can think about having devices that weigh single molecules."

But to identify proteins by weight, the scales will have to become another 1000 times more precise, capable of weighing yoctograms (10^-24)g), or individual hydrogen atoms.