This lesson provides a clear and structured introduction to composite functions, designed for IGCSE and GCSE students. It builds understanding step-by-step, starting from the definition of a function and progressing to composite functions, including advanced ideas such as self-composition and reciprocal relationships where the product of two functions equals 1. The worksheet includes worked examples, exam-style practice questions, and homework with full solutions, ensuring strong conceptual understanding and exam readiness. Its logical progression, clean layout, and differentiated practice make it ideal for classroom teaching, revision, or independent study.