Nishijima's Theorem is a principle in particle physics that relates the properties of particles to their symmetries. It connects the concept of baryon number and lepton number with the charge conjugation symmetry, helping to classify particles based on their behavior under certain transformations. This theorem is particularly useful in understanding the interactions of quarks and leptons. The theorem was formulated by Yoshio Nishijima in the 1950s and has implications for the conservation laws in particle interactions. It provides a framework for predicting how particles will behave in high-energy collisions, contributing to the development of the Standard Model of particle physics.