‘Epilogue: Final frontiers?’ considers undersea and space exploration. Jacques-Yves Cousteau claimed the oceans were the last frontier of our planet. The Cold War race to the moon took exploration into space. Are these the final frontiers? For all the different forms it takes in different historical periods, for all the worthy and unworthy motives that lie behind it, exploration—travel for the sake of discovery and adventure—seems to be a human compulsion, a human obsession even; it is a defining element of a distinctly human identity, and it will never rest at any frontier, whether terrestrial or extraterrestrial.