The lowest weight that can be detected today is 100 grams, i.e. 0.1 trilions per gram. At this level, its detection means detecting the mechanical movement of what you want to weigh. Sensors that work with semiconductors are normally used, but some physicists at the Caltech institute have managed to do so by another means: a metallic nanoxafla. This makes the method more precise than any other, and can also be used at room temperature, unlike the semiconductor.