Euclid is known for writing The Elements, one of the most influential works in mathematics. The Elements laid out the basics of geometry and number theory through definitions, postulates, and 465 theorems proved through deduction. It covered areas like plane geometry, solid geometry, and early number theory. Euclid divided The Elements into 13 books covering topics such as commensurable and incommensurable lines. The work was widely studied and established Euclid as the "father of geometry."