Europe's rich history is traditionally divided into four major periods, beginning with early modern humans around 48,000 years ago and the Neolithic advent of agriculture and megalithic structures like Stonehenge. Classical Antiquity (800 BC – AD 500) saw the rise of ancient Greece and the unifying power of the Roman Empire, whose fall in AD 476 marked the beginning of the Middle Ages. This era featured Charlemagne's empire, Viking migrations, the Crusades, and the devastating Black Death, concluding with the Renaissance. From AD 1500, the modern era brought profound changes like the printing press, Reformation, Age of Discovery leading to colonization, and the Industrial Revolution. The 20th century was defined by two World Wars, the Holocaust, and the Cold War's division of the continent, culminating in the eventual formation of the European Union and current geopolitical challenges including the Russian invasion of Ukraine.