The Second Great Lesson in Montessori's Cosmic Education, also known as The Story of Life, builds upon the First Great Lesson by exploring the formation of Earth and introducing students to the Long Black Line, the Clock of Eras, and the Timeline of Life. This lesson tells the story of how Earth transformed into a habitat for a diverse range of life forms, from microscopic organisms to humans. Originally, the Long Black Line was used as a lesson in humility for students. Together, Montessori's Five Great Lessons provide children with a contextual understanding of their identity, origins, and unique cosmic task.