Who was the Zodiac Killer who terrorized residents of California during the 1960s and 1970s? The answer is still unknown. Readers take an in-depth look at the investigation that continues to fascinate Americans, discovering the details of the crimes and the search for the person who committed them. Additional information is presented through engaging sidebars and eye-catching fact boxes. Historical and contemporary photographs, including primary source...

What kinds of machines do mechanics fix? How can you become a mechanic? The answers are waiting for readers to discover as they explore this exciting and important career. Eye-catching fact boxes accompany the detailed main text. A graphic organizer provides an additional avenue through which readers can discover information about mechanics and how to become one. Colorful photographs of mechanics at work give readers a clear sense of what this career...

The research and discoveries made by French chemist and microbiologist in the 1800s have benefitted mankind well into the 21st century. He proved microorganisms cause diseases, and developed vaccines. American scientist Henrietta Swan Leavitt contributed to the science of astronomy, specifically regarding the brightness of stars. Inside this guide, readers will explore the lives and discoveries of these historical figures as well as many other notable...

German naturalist Alexander von Humboldt helped popularized science texts with his book Kosmos, published in five volumes between 1845 and 1862, which gives an understandable account of the structure of the universe as known at the time. Around the same time, Gregor Mendel famously studied pea plants and laid the foundation for the modern science of genetics. Readers will be amazed by the detailed biographies of these and many other notable scientists,...