In this talk, I will present two topics in atmospheric ice microphysics that have recently been studied at the Mainz vertical wind tunnel laboratory. First, I will introduce our experiments on the fragmentation of ice particles due to collision, which is one of the most important secondary ice production mechanisms in the atmosphere. In the second part of my talk, I will provide the results of our wind tunnel experiments in which we compared the melting behavior of hailstones with spherical and natural-like shapes. We examined factors such as fall speed, meltwater content, and the distribution of shed drop sizes.