Cartoon of two possible trajectories through space and time of pebble super-particles (1 and 2). Both super-particles start out in the outer disk with a small typical particle mass. The physical particles represented by the super-particles grow until they reach a size where radial drift becomes faster than growth, and they start to drift inward. Planetesimal formation occurs outside the snowline as well as in the dry inner disk. See text for a more elaborate description.