Pierre de Fermat and Blaise Pascal were two 17th century French mathematicians. Fermat effectively invented modern number theory and made important contributions to calculus and probability theory. He formulated Fermat's Last Theorem which took over 350 years to prove fully. Pascal made advances in projective geometry and probability theory. Through correspondence, he and Fermat established the foundations of probability by developing the concept of equally probable outcomes and using it to solve problems like the Gambler's Ruin. Pascal is also known for Pascal's Triangle which demonstrates patterns in binomial coefficients.