Simon Portegies Zwart leads since 2009 an interdisciplinary research team on Computational Astrophysics at Leiden Observatory, focusing on understanding the universe through simulation while developing algorithms and tools to handle its complexity and multi-scale nature. He founded the IAU Commission C.1B on Computational Astrophysics, as well as the AMUSE project, and was honored by the IAU for naming steroid 12946 ""portegieszwart"". Steve McMillan is the head of the department of physics at Drexel University and his research interests lie in stellar dynamics and computations of stellar systems. Both authors have dedicated extensive amounts of time to this book and continue to work on AMUSE as an ongoing project. Steven Rieder is a Scientific Research Software Engineer at the Anton Pannekoek Institute for Astronomy at the University of Amsterdam. His interests lie in the formation and evolution of dense stellar systems, the development of software that enables such research, and in science visualisation.