What is the exposition in the story of The mustache by Robert comier?

In "The Mustache" by Robert Cormier, the exposition introduces the protagonist, a teenage boy named Mike, who is grappling with his identity and the transition into adulthood. The story begins with Mike deciding to grow a mustache, which serves as a symbol of maturity and change. This decision leads him to confront his relationships, particularly with his grandmother, who struggles to recognize him as he attempts to assert his new persona. The initial setup establishes the themes of perception, family dynamics, and the challenges of growing up.