A recent publication announced some remarkably fine new measurement of the gravitational attraction between extremely small objects. Also reported in Scientific American, the Aspelmeyer group at the University of Vienna has measured gravitational interactions between millimeter scale objects. You can read all the details in the papers below.
B. Brubaker, Physicists Measure the Gravitational Force between the Smallest Masses Yet, Scientific American, 2021 March 10
Westfal, Hepach, Pfaff, & Aspelmeyer, Measurement of gravitational coupling between millimetre-sized masses, Nature, 20201 March 10
Aspelmeyer Group at the University of Vienna
If you’re discussing this kind of measurement in class, check out our model of the classic Cavendish Experiment, E1-01 in the demonstration collection.