From Athens, Aristotle traveled to Assos, where he was received warmly by the ruler Hermias of Atarneus. Many believe he was acting as an ambassador for Philip of Macedonia, and he was certainly treated as such. He married Pythias, the niece and adopted daughter of Hermias, who was probably about 18 at the time. They had one child, a daughter also called Pythias, but the elder Pythias died about 10 years after their marriage.
Hermias had gathered group of philosophers on Assos. Aristotle became the leader of this group. Thanks to his father, he was very interested in anatomy and biology and was a great observer. Aristotle and his group began to collect observations while in Assos, in particular in zoology and biology. He also probably began writing Politics during these years as well as On Kingship, which hasn't survive to this day. Unfortunately, politics once again played a part in Aristotles next move. When the Persiand attacked Assos and captured Hermias, Aristotle escaped with many of his scientists to the island of Lesbos. They remained there for about a year, continuing their research.