In 2018, Italy's Morandi Bridge collapsed, tragically killing 43 people. For 50 years, the iconic bridge had withstood the elements—and stress from ever-increasing traffic. What went wrong that fateful day? And how can new engineering technology protect bridge infrastructure to prevent such tragic failures in the future? Through eyewitness testimony, expert interviews, and dramatic archival footage, NOVA investigates the Morandi disaster and other deadly bridge collapses across the United States.

Sixty-six million years ago, an asteroid wiped out the dinosaurs in a fiery global catastrophe. But we know little about how their successors, the mammals, recovered and took over the world. Now, hidden inside ordinary-looking rocks, an astonishing trove of fossils reveals a dramatic new picture of how rat-sized creatures ballooned in size and began to evolve into the vast array of species—from cheetahs to bats to whales to humans—that rule our planet today.