Sketch of the planetesimal formation mechanism we suggest. Thanks to the radial variation in turbulence efficiency, the position of the collision regimes is shifted in terms of particle size. The dust aggregates can grow to larger sizes in the dead zone than in the MRI active zone. The big particles grown in the dead zone drift inwards through the bouncing regime, to the location of the pressure trap, and some of them can continue to grow via sweeping up the small particles halted by the bouncing barrier.