Charli Explores STEM #3. Transitional Chapter Book. Grades 2-3. Approximately 2,500 words, 96 pages. Encourages girls to pursue STEM education and careers. When Charli meets an engineer at Career Day, she can't stop thinking about what it would be like to be an engineer herself. Soon, she is lost in an engineering daydream, designing a tracking device that will let a rescued dolphin return to the ocean. But will creating a device that can attach to the dolphin and work underwater be more than Charli can handle?.