An active-passive system is composed of an ensemble of active out-of equilibrium agents, interacting with passive ones. This could be the interior of a cell, with molecular motors creating flows which transport passive (as in: non-active) material; or it could be non-motile bacteria buffeted around by motile ones (see also bacterial hitchhiking!). In all of these cases, the active “bath” changes significantly the stochastic properties of the passive components. Together with Horacio Serna, Miguel Barriuso, Ignacio Pagonabarraga and Chantal Valeriani, we studied one example of these properties, where activity leads to an enhanced sorting of the system. The paper is out now on Soft Matter and we also got one of the two issue covers!