How life began on Earth is the question driving this NOVA episode, hosted by astrophysicist Neil deGrasse Tyson. The search starts underground rather than in a lab: two miles down in mine shafts where microbes survive locked inside rock, in cave systems where the water is as acidic as battery fluid, and on the Pacific seafloor where toxic gas vents support organisms that never see sunlight. Each of these microbes becomes a stand-in for what the planet's first life might have looked like, since anything that can survive there might have survived the young Earth's own hostile chemistry. Tyson then widens the search off-planet, examining chemical traces some scientists read as signs of ancient biology in rocks and meteorites roughly three billion years old, a claim the film treats as live and contested rather than settled. The episode moves between geologists, astrobiologists, and chemists rather than resolving into one answer, tracing the current scientific argument over where life's first spark actually came from.