Physicists from École Normale Supérieure and Paris Science and Letters University in France have proven theoretically that active sieving, as opposed to its passive counterpart, can improve the separation abilities of filtration systems. These new views on how active sieving could improve systems such as those used in water purification and dialysis were reported this week in The Journal of Chemical Physics. Active sieving also has the potential to filter molecules based on movement dynamics, opening up a whole new avenue in the field of membrane science based on the ability to tune osmotic pressure.