The Effect: When Europeans began to explore the Americas, they found many plants they had never seen nor heard of before. They took many of these back to Europe, Asia, and Africa, where the foods soon became an essential part of people's staple diets - e.g. potatoes, tomatoes, chilis, and cacao beans (made into chocolate) - and the less edible tobacco spread, leaving its own trail of ruin behind it. This was not just a one-way exchange, though: livestock were brought over to the Americas by the Europeans and bred quickly, suddenly creating a whole new population of pigs, cows, sheep, chickens, rabbits and horses.