Few things seem as irreversible as death, whether for an individual or a species. But what would happen if death was reversible, if we could bring back to life something similar to the species that became extinct in the past? Recent developments in various techniques in molecular biology, among them cloning, synthetic genomes and genetic editing, have led to the emergence of a field of research that is in pursuit of de-extinction. This is a controversial ambition that presents far-reaching scientific, ethical, economic and social challenges. Even so, its proponents defend it as one of the possible ways to restore ecosystems and even fight against climate change. Explained over the course of this book are the possibilities for de-extinction and how they could transform the global ecosystem in the future.