Immigration to the United States explains the immigration experience of four different groups of people—the Irish, the Chinese, the Mexican, and the German Jews. While each of the four books focuses on a different cultural group and its unique immigration experience, the same key concepts are developed across books to help students focus on the big ideas. The theme explores some of the reasons people immigrate, the challenges they face, and how the immigrants influence the life and culture of their new home. Students use the specific content and vocabulary within each book to discuss and examine these big ideas, or Key Concepts. The Theme Set Program is designed for differentiated instruction. Each Theme includes four books written at four different reading levels.