Most people today think of chocolate as something sweet to eat or drink that can be easily found in stores around the world. It might surprise you that chocolate was once highly treasured. Researchers at the University of Pennsylvania recently released a study. It suggested that people in Central and South America first gathered the cacao plant much earlier and for a different use than experts once thought. ① The researchers examined the chemistry of substances found in ancient clay containers that were over three thousand years old. They discovered that the substance came from an alcoholic drink made from the fruit of the cacao plant. The researchers believe it was the interest in cacao as an alcoholic drink that led to the use of its bitter seeds to make what is now known as chocolate. ② Historians believe the Maya people of Central America first learned to farm cacao plants around two thousand years ago. The Maya took the cacao trees from the rainforests and grew them in their gardens. They cooked the cacao seeds, and then crushed them into a soft paste. They mixed the paste with water and flavorful spices to make an unsweetened chocolate drink. The Maya poured the chocolate drink back and forth between two containers so that the liquid had a layer of bubbles, or foam. ③ Cacao and chocolate were an important part of Maya culture. There are often images of cacao plants on Maya buildings and art objects. Ruling families drank chocolate at special ceremonies. And, even poorer members of society could enjoy the drink once in a while. Historians believe that cacao seeds were also used in wedding ceremonies as a sign of the union between a husband and wife. The Aztec culture in current day Mexico also prized chocolate. But, the cacao plant could not grow in the area where the Aztecs lived. So, they traded to get cacao. They even used cacao seeds as a form. of money to pay taxes or give as holy offerings to the gods. Only the very wealthy people in Aztec societies could afford to drink chocolate because cacao was so valuable. Some experts believe the word for chocolate came from the Aztec word 'xocolatl' which in the Nahuatl language means “bitter water”. Others believe the word 'chocolate' was created by combining Mayan and Nahuatl words. The explorer Christopher Columbus brought cacao seeds to Spain after his trip to Central America in 1502. But it was the Spanish explorer Hernando Cortes who understood that chocolate could be a valuable investment. In 1519, Cortes arrived in current day Mexico. He believed the chocolate drink would become popular with Spaniards. After the Spanish soldiers defeated the Aztec empire, they were able to seize the supplies of cacao and send them home. Spain later began planting cacao in its colonies in the Americas in order to supply the large demand for chocolate. The wealthy people of Spain first enjoyed a sweetened version of the chocolate drink. Later, the popularity of the drink spread throughout Europe. The English, Dutch and French began to plant cacao trees in their own colonies. Chocolate remained a drink that only wealthy people could afford to drink until the eighteenth century. During the period known as the Industrial Revolution, new technologies helped make chocolate less costly to produce. What is the main idea of this passage?