Pairs of skyrmions—tiny whirlpools that emerge in some magnetic materials—might be able to self-propel, a behavior reminiscent of that of active-matter systems such as motile bacteria.

In nature, the collective motion of birds and fish can generate impressive dynamics and unique structures, as seen in flocks of starlings and shoals of sardines. The science of active matter studies such complex behaviors across a wide range of scales and origins [1], and it has attracted growing interest over the past three decades. Active matter encompasses not only living things but also inanimate objects. Examples include active colloids [2] and active liquid crystals [3] that are able to self-propel—that is, move by themselves powered by internal energy sources. Now Clécio de Souza Silva and colleagues at the Federal University of Pernambuco in Brazil have suggested an intriguing addition to the active-matter catalog: coupled pairs of skyrmions, whirlpool-like spin arrangements that emerge in certain magnetic materials.