This learning resource focuses on the concept of cosmic expansion using a balloon model. It outlines safety procedures for handling balloons in a lab setting, emphasizing the importance of protective eyewear and careful handling to prevent injuries. The session aims to illustrate how the surface of an expanding balloon can model the universe, where the balloon surface represents the universe itself and the dots on the surface symbolize galaxies moving apart from each other. It also introduces the Cosmological Principle, which posits that the universe appears uniform for all observers regardless of their location. At the end of the session, students are encouraged to reflect on the day's goal and articulate how the model explains cosmic expansion.