Ask for chocolate 5,300 years ago in ancient Ecuador and you would have been handed a bitter, lightly alcoholic drink fermented from fruit pulp. This episode follows cacao from sacred Mesoamerican currency and frothy ceremonial drinks to Europe’s elite and the industrial inventions that created the modern chocolate bar.

We explain Van Houten’s hydraulic press, the conching process that grinds particles below what the tongue can detect, and the crystal science of tempering that gives chocolate its gloss and snap. We also separate real health effects from myths, explain why chocolate is toxic to dogs, and examine child labor and the limits of fair trade in the 50 billion dollar cocoa industry.

• How the Olmec, Maya, and Aztec used cacao as a drink, tribute, and currency
• The contested origin of the word chocolate and the Maya chicolatl theory
• Van Houten’s cocoa press, the first mass-market bars, and conching below 20 micrometers
• Form V cocoa butter crystals, tempering, and why old chocolate blooms
• Heavy metals, theobromine toxicity in pets, and the economics of West African cocoa farming