Themes: 3D Printing, Science, Technology, Nonfiction, Tween. 3D printing has made some fascinating developments in recent years. It has been around since the 1980s, but technology has improved dramatically. Now, 3D printers are used in business, medicine, cooking, fashion, and more. Red Rhino Books Nonfiction is the first Hi-Lo children's nonfiction series at a first-grade reading level for students in grades 4–7. Visually appealing fullcolor photographs and illustrations—along with fun fact boxes—keep these books flowing. Also includes prereading comprehension questions along with a 20-word glossary for further reading support.