This Festschrift is a tribute to Susan Stepney’s ideas and achievements in the areas of computer science, formal specifications and proofs, complex systems, unconventional computing, artificial chemistry, and artificial life. All chapters were written by internationally recognised leaders in computer science, physics, mathematics, and engineering. The book shares fascinating ideas, algorithms and implementations related to the formal specification of programming languages and applications, behavioural inheritance, modelling and analysis of complex systems, parallel computing and non-universality, growing cities, artificial life, evolving artificial neural networks, and unconventional computing. Accordingly, it offers an insightful and enjoyable work for readers from all walks of life, from undergraduate students to university professors, from mathematicians, computers scientists and engineers to physicists, chemists and biologists.