In the beginning, École Polytechnique was exclusively reserved for male students, which prompted Sophie Germain to adopt the identity of a former student, Antoine Auguste Leblanc, in order to receive mathematics lessons by mail. She sent her answers and observations to Joseph-Louis Lagrange, who, impressed by the student’s intelligence, summoned for "him" and discovered Germain’s trickery. Professor Lagrange became Germain’s friend and mentor, which helped her launch her scientific career. Her research and work focused mainly on number theory and the solution of Fermat’s theorem, and the elasticity of bodies. In 1816, her elasticity research led to her winning a prize from the French Academy of Sciences and becoming the first woman permitted to attend sessions at the Institut de France.