Some bacteria are helpful, while others can make us very sick. Readers learn the difference in this engaging and educational look at a popular biology curriculum concept. The clear main text is paired with full-color photographs that take readers under the microscope to see various kinds of bacteria up close. Graphic organizers add another helpful visual element, and sidebars expand on important topics. Readers are challenged to think critically about what they've learned with questions at the end of every chapter. They're also shown a number of ways to protect themselves from bacteria that can cause disease.