Freezing sperm is relatively simple and only requires a sperm sample to be produced through ejaculation. The sperm sample is then divided into smaller portions and frozen in liquid nitrogen at -196°C.
Freezing eggs and embryos requires an IVF-type procedure involving ovarian stimulation and an egg pickup. For egg-freezing, only mature eggs are frozen. For embryo-freezing, mature eggs are fertilised with sperm to make embryos, which can then be frozen on either Day2/3 or Day 5/6 of development. See my section on IVF/ICSI Treatment for more information.