— Understanding Thresholds of Complexity
— Not Too Hot, Not Too Cold

— Where Did Everything Come From?
— From Many Beginnings, Many Stories

— In An Instant, Everything Happens
— A Mysterious Hiss From the Heavens

— Tiny Knots and Wrinkles in the Young Universe
— Gravity

— The Birth of Matter and Elements

— Complexity Explodes into the Universe
— Collective Learning

— Activity: Periodic Table

— A New Day Begins
— Activity: The Lifecycle of our Sun

— How Did the Planets Form?

— What Did the Young Earth Look Like
— Finding Earth
— Astronomers
— The Speed of Light

— Out With the Bad, In With the Good
— Activity: Goldilocks Conditions

— The Massive Supercontinent Breaks

— A Case for Pangaea
— Together, Decades Apart, They Proved It

— From Chemicals to Consciousness
— The Earliest Life Forms

— Activity: Mass Extinctions
— Layers of History
— Solving the Dinosaur Mystery

— The Double Helix Discovery
— Baffling DNA
— Activity: Shared DNA

— 3.5 Billion Years Old and Growing

— Using Tools, Shelter, and Fire

— Activity: Human Migration
— Writing and Saving Knowledge

— Complex Civilization Begins
— The Rise of Civilization

— Did Religion Sow the Seeds of Civilization

— A New, More Complex Society is Born
— Activity: Ancient Cities

— Taking a Trip Down the Silk Road

— Feeding the Empire

— About Two Hundred Years Ago to the World Today
— Fuel for the Ages
— Activity: Population and Energy Consumption
— Climate and Atmosphere

— Trade, Fuel, and Globalization
— Activity: Inventions of the Modern Era

— Ecological Impact

— Can the Past Foretell the Future
— Activity: Poll: Our Future