Scientists have succeeded in making a scale that can weigh something as small as a zeptogram. This is about the size of protein molecule. This is useful because you can now identify a molecule (or at least narrow down the possibilities a lot) by weighing it.
What's neat about this is that the principle is pretty easy to understand. What they did was make a tiny "diving board", and attach an electromagnetic vibration sensor (similar to what is in the mouthpiece of a telephone) to it. In the natatorium, a big person makes the diving board vibrate differently than a small person, and the same thing happens at the molecular level. Put a molecule of known weight on the diving board, calibrate the sensor, and ouila - a scale.
I know what you're saying - they're just making up metric prefixes at this point. Maybe so, but for perspective in declining order by one thousandths the measures of weight are the gram, milligram, microgram, nanogram, picogram, femtogram, attogram, attaboy, and zeptogram, and yoctogram. A yoctogram is about 60% of the weight of a proton or neutron.