In the 1980s and 1990s, in keeping with the greater sophistication of its graphic imagery and in connection with movements in popular fiction, manga began to take on grand, sometimes even cosmic, philosophical themes, interrogating the nature of reality, the essential meaning of the human life, and its insecure place in the interconnected realm of existence. Tales of apocalypse, and post-apocalyptic, dystopian worlds, of humanoid cyborgs and alternate realities, combined with theories from physics and philosophy, are prevalent in the popular manga of this time. Deep doubt about the future of humanity is seen in works such as Fist of the North Star, Akira, and Nausicaä of the Valley of the Wind, all of which take place after the use of catastrophic weaponry redefines life on Earth, while X deals with an apocalypse about to occur. Ghost in the Shell focuses on the relation between human beings and machines in a future of advanced cyberization, questioning what it is (if anything) that makes them different. An underlying theme throughout all of these manga is resistance to the status quo and social norms that have brought humanity to the brink of its own destruction.