The practical understanding of fission track methods described here has been developed over many years and has benefited from discussions with many colleague researchers and students in the Melbourne Thermochronology Group and elsewhere. These are too numerous to name individually, but it has been my pleasure to work with all of them and to share a mutual fascination with fission tracks and, particularly, with what they can tell us about the history of the Earth. Barry Kohn made valuable suggestions on an earlier draft and parts of Chapter 5 have drawn on a summary from Wayne Noble’s PhD thesis. Work in the Melbourne Fission Track Laboratory has been supported over many years by grants from the Australian Research Council, the Australian Institute of Nuclear Science and Engineering, La Trobe University, the University of Melbourne, the Australian Geodynamics Cooperative Research Centre, and the AuScope and AGOS National Research Infrastructure programs. All of this vital support is gratefully acknowledged.