Any phenomenon that persists at various scales is bound to excite a physicist's curiosity," says Denis Bartolo, a faculty member at the Ecole Normale Supérieure in Lyon, France, and lead author of an article published by Nature magazine last November, in partnership with fellow researchers at ESPCI Paris Tech and the National Centre for Scientific Research. Indeed, it was the Hungarian physicistTamás Vicsek who kindled the community's interest for this natural mystery in 1995.The French scientists adopted a very basic approach to modelling their "starlings". In their system millions of tiny plastic beads five micrometres in diameter swim through a conducting liquid suspension to which an electric field is applied. Opposite electrical charges accumulate on either side of a bead. This creates a dipole that, just like the needle of a compass, tries to line itself up with the "north" – in the present case, the constant electric field. The bead starts turning, never stopping because the charges keep circulating, upsetting the dipoles. Georg Quincke discovered this rotation effect in 1896 but this is the first time anyone has thought of using it to study collective motion.