In the movie Alien, the title character is an extraterrestrial creature that can survive brutal heat and resist the effects of toxins. In real life, organisms with similar traits exist, such as the "extremophile" red alga Galdieria sulphuraria. In hot springs in Yellowstone National Park, Galdieria uses energy from the sun to produce sugars through photosynthesis. In the darkness of old mineshafts in drainage as caustic as battery acid, it feeds on bacteria and survives high concentrations of arsenic and heavy metals. How has a one-celled alga acquired such flexibility and resilience?