Paper: Asteroid Families, Old and Young Volume: 107, Completing the Inventory of the Solar System Page: 45 Authors: Farinella, P.; Davis, D. R.; Marzari, F. Abstract: Some recent progress is reported on the long--standing problem of estimating asteroid family ages, namely of dating in a reliable way the impact break--up or cratering events which formed the observed families. Recent results on this issue come from improved estimates of asteroid collisional lifetimes, from numerical modelling of the post--formation erosion'' of families, from a chaotic chronology'' method based on dynamical diffusion--like effects in proper element space, and from recent {\it Galileo} observations of (243) Ida, one of the largest Koronis family members, and its satellite Dactyl.