History of monomers in a disk with ﹩\alpha ={10}^{-2}﹩ in the midplane at ﹩r=5\;\mathrm{au}﹩ and a local dust-to-gas ratio of 0.01. Left: aggregate sizes in which the monomer is incorporated as a function of time. During 10,000 years, many sticking, erosion, and fragmentation events occur, and the small grain we are following is part of many different aggregates. Right: normalized histogram of the cumulative time grains spent inside bodies of size s, averaged over 500 monomer histories of 10,000 years each (excluding the first 1000 years). Overall, the histogram is in good agreement with the mass-weighted background size-distribution.