In 1519, one of the great earth-shattering events in all of human history occurred.
Hernán Cortés, along with a few hundred Spaniards and local Native American tribe allies that they'd met along the way, went into the city of Tenochtitlán and encountered one of the most beautiful cities/places they had ever seen. The Europeans were marveled at this sophisticated civilization known as the Aztecs, who had a city that was more beautiful than Rome or Paris back on their continent. Despite such an established, organized, and intelligent group of people as the Aztecs were, the Spaniards were consumed by greed for gold and their fervent belief that Catholicism was the only true religion above all other creeds. Their goal/mission was to impose their ways over whomever they encountered.
The Aztecs, were a warrior like peoples, with a highly developed agricultural system that included crops such as corn, tomatoes, chocolate, and avocados. They had tremendous architectural knowledge and built pyramids and temples to honor their emperor and worship their gods. They established a glorious empire in central Mexico which created many enemies in the surrounding areas who were jealous and resentful of Aztec power. Most notably (and to the horror of the Spaniards), was the common practice of human sacrifice, where prisoners would be offered to the gods by having their hearts cut out in public ceremonies.
The Aztecs had foreseen their destruction/doom. Their religion/mythology had predicted the return of their white-skinned bearded God Quetzalcoatl from the East someday. Was it just sheer luck? A fortuitous coincidence? Regardless, the white-bearded pale men did arrive from the East as had been foretold. Cortés brought with him horses, weapons, Christianity, and a tenacity to conquer. He took in a mistress named La Malinche, a woman considered to be a traitor to the Mexican people, and she became the mother of the "first" mixed race child and his translator with the Aztecs. The moment that Cortés met the Aztec Emperor Moctezuma, was one of the watershed events of all time, a meeting of very alien cultures that would soon mix and influence us to this very day.
The sieges and attacks by the Spaniards took some two years to unfold, but by 1521, all hope was lost for the great Aztec Empire. Both sides lost great numbers of men in battle, but when all was said in done, European technology and their diseases (which the natives had no immunity to) won the day. Spain was beginning to add massive territory to her growing unstoppable empire and altering the face of the modern day world forever. Her language, culture, and religion were to become cemented in these new lands.
The cultural/global impact of this conquest, this meeting, cannot be overstated.