Classic Sci-Fi Tropes

Artificial Human, creatures not unlike us, but created rather than born. Not to be mistaken with Killer Robots.

Early Space Flight, involving fantastic ideas of what might be "out there" in the universe before 1960.

Killer Robots, which were created for no other purpose than to destroy humanity, or who become sentient and/or realize that humans are the cause for all problems.

Lost Worlds, where a strangely advanced culture or formerly-extinct or giant creatures abide.

Nature Hero, where a man lives/grew up in the wild, and feels more comfortable with animals than people. AKA Lost Heir or Wild Child or Jungle Princess.

Rip Van Winkle, where the protagonist falls asleep and wakes in a very different world. AKA Slept Through the Apocalypse or Cold Sleep, Cold Future.

Time Travel, where science has made travel through time (whether forward or backward) possible, and someone uses it. Often involves Dystopias when traveling forward, occasionally involves Mad Scientists as the inventors.

Fantastic Journey, in which the protagonist finds himself on a great adventure, often in a world he did not know even existed before. See also Lost Worlds, Rip Van Winkle, Dystopias, Time Travel, and Early Space Flight.

Dystopia, a world that has become decadent or is in decline, often with a very regimented societal structure, often involving slavery, cannibalism, or other dark subjects. Usually set in a future time, in a city setting. Not to be confused with Future or Post-apocalyptic stories, though it can involve such ideas.

Note: Post-apocalyptic stories did exist pre-1940's nuclear hysteria, but not in as great quantity as after. Most focused on the dystopian aspects.

Mad Scientist, where science and the evils it propagates are the main plot point of the story. AkA Evil Genius. Also a Character Archtype.

Alien Invasion, where aliens come to Earth to conquer or destroy us utterly.

The Vanished, where the Protagonist, sometimes a Mad Scientist, finds himself separated from the rest of the world by circumstances beyond his control. Often features invisibility, shrinking, or alien abduction.