Aristotle is one of the "big three" in ancient Greek philosophy, along with Plato and Socrates. (Socrates taught Plato, who in turn instructed Aristotle.) Aristotle spent nearly 20 years at Plato's Academy, first as a student and then as a teacher. After Plato's death he traveled widely and educated a famous pupil, Alexander the Great, the Macedonian who nearly conquered the world. Later Aristotle began his own school in Athens, known as the Lyceum. Aristotle is known for his carefully detailed observations about nature and the physical world, which laid the groundwork for the modern study of biology. Among his works are the texts Physics, Metaphysics, Rhetoric and Ethics. He was succeeded at the Lyceum by his student Theophrastus.