What does Elie and his father go through after arriving at Birkneau

Upon arrival Eliezer and his father are separated from his mother and sisters; they will never see them again. They go through the first of many "selections" where they need to prove they are worth not killing. Both Elie and his father see the open pit where they burn children and babies. THey proceed to barracks where they are stripped, shaved and disinfected. All of this is of course a nightmare beyond comprehension.