When you read the word “ancient,” you likely think of something old and outdated. But you may be surprised to hear that many of the ideas and institutions that came from ancient Greece still exist today. We have the ancient Greeks to thank for things like present-day democracy, libraries, the modern alphabet, and even zoology.

Here are some notable Greek figures—from philosophers to mathematicians and scientists—and how they have shaped the world we know today.

Socrates

Socrates was one of the most prominent ancient Greek philosophers. Socrates spent the majority of his life asking questions, always in search of the truth. He is responsible for developing what is known as the Socratic method, a technique still used by professors in law schools today. Instead of lecturing the students, professors will ask them a series of thought-provoking questions. These questions help the students think critically, and they are meant to elicit underlying presumptions and ideas that could be influencing the way a student views a case. Socrates engaged his students in this same fashion. He did not leave any written record of his life or ideas, so most of what we know about Socrates was written by one of his students, Plato.

Plato

Thanks to Plato, we know a lot about Socrates. Nevertheless, Plato made his own important contributions. Born around 427 B.C.E., Plato influenced Western philosophy by developing several of its many branches: epistemology, metaphysics, ethics, and aesthetics. Plato was also a prominent writer. One of his most famous writings is the Republic. In the Republic, Plato examines justice, its role in our world, and its relationship to happiness, themes familiar to the founding fathers of the United States. Plato is also famous for being the teacher of another important philosopher, Aristotle.

Aristotle

Aristotle is still considered one of the greatest thinkers in the areas of politics, psychology, and ethics. Like Plato, Aristotle was a prolific writer. He wrote an estimated 200 works during his lifetime; 31 of them are still admired and studied today. Aristotle thought a lot about the meaning of life and about living a moral life. Immensely curious, he also studied animals and sought to classify them into different groups, laying the foundation for zoology today. Through his writing about the soul and its properties, Aristotle laid the foundation for modern psychology. He was also called on to tutor King Philip II of Macedon’s son, Alexander, who would later come to be known as Alexander “the Great.”

While the great philosophers are well known, there were many other great Greek political and military leaders who had an impact on the world.

Alexander the Great

Born to notable military leader King Philip II, Alexander III of Macedon proved early on that he was destined for greatness. At a young age, Alexander learned to fight and ride, famously taming the wild horse Bucephalus at age 12. Only a few years later, at age 18, Alexander got his first chance to fight in a war and helped defeat the Sacred Band of Thebes during the Battle of Chaeronea. Soon he took over the throne his father once held and continued to prove himself a strong and able military mind. Alexander eventually created an empire stretching from Macedon across the entire Middle East to the frontiers of India. By 323 B.C.E., Alexander ruled over an enormous amount of land a feat that caused historians to give him the nickname Alexander “the Great.”

Pericles

At the other end of ancient Greece was another strong leader working to grow the city of Athens. His name was Pericles. Pericles was born over 100 years before Alexander the Great, but he had a similar background. He came from a prominent family in Athens and had a war hero for a father. Pericles did much to help the culture of Athens flourish. Consistently surrounded by the arts, one of the first things he did was to sponsor the playwright Aeschylus. He also helped fund the building of the Parthenon, a temple dedicated to the goddess Athena that still stands today. Soon Pericles made his way into politics and was eventually elected as one of Athens’ leading generals. Like Alexander, Pericles was military minded and led many successful military campaigns. As a statesman, he contributed in many ways to what is considered the golden age of the city of Athens.

These philosophers and the Greek military and political leaders left their mark on both ancient Greece and the present-day Western world, but there were also famous mathematicians and scientists whose work and ideas are still popular today.

Pythagoras

If you’ve ever tried to find the area of a right triangle, you’ve likely had to use something called the Pythagorean theorem, which is named after the mathematician Pythagoras. This theorem is one of the biggest contributions that Pythagoras made to mathematics. Pythagoras used numbers and mathematics to seek meaning in life. He even created a religious order in which the members focused on philosophy and math in order to find personal salvation.

Hippocrates

Modern medicine has been heavily influenced by the work of Hippocrates, an ancient Greek physician. The methods attributed to Hippocrates are compiled in 60 medical books known as the Hippocratic corpus. It is from these books that we have learned what was done in Hippocratic medicine. This practice of medicine included adopting a healthy diet and engaging in physical exercise—ideas still espoused to the public today. The corpus also included information about the importance of recording case histories and treatments, another practice essential to modern medicine. Hippocrates is best known for the wisdom contained in the Hippocratic oath, modern versions of which still govern the ethical principles by which new doctors promise to observe when practicing medicine.

Though these prominent Greeks lived centuries before us, they have left a brilliant legacy. By building on their hard work and great ideas, we’ve been able to establish the thriving world we live in today.