Leonhard Euler

Leonhard Euler was the most prolific mathematician in history, producing an staggering volume of work that touched almost every branch of mathematics. He introduced much of the modern mathematical notation we use today, including the concept of a function, the base of natural logarithms 'e', and the use of 'i' for the imaginary unit. His solution to the Seven Bridges of Königsberg problem founded graph theory and topology. Euler's work is so foundational that it is impossible to study advanced mathematics without encountering his theorems, formulas, and notations on a daily basis.