Physicists in Germany have used an atomic interferometer to perform the most accurate ever test of the equivalence principle at the level of atoms. Sebastian Fray and colleagues at the Max Planck Institute for Quantum Optics in Garching and the universities of Munich and Tuebingen compared the acceleration of two isotopes of rubidium in the Earth's gravitational field (arXiv.org/abs/physics/0411052). As expected the atoms accelerated at the same rate.