Gr 1--3--Wells presents information about DNA and how it makes each person unique. Although the title refers specifically to molecules, the focus of the book is the genetic system, moving from cells to molecules, chromosomes, and genes. A conversational tone addresses readers directly, asking questions such as what makes humans different from cats and from other human beings. Wells describes DNA as being an instruction manual, likening the structure to a much more complex version of instructions for building a robot. A small girl with tan skin and black hair, along with her ginger cat, act as hosts to the text, hanging off a double helix or sitting among towers of books. It's a friendly presentation, even as the narrative never veers away from nonfiction. The digital images support the ideas in the text, such as demonstrating the lengths of DNA strands by wrapping them around the Earth. Diagrams are useful and contribute to understanding of the text that, although simple, presents complex ideas. VERDICT This straightforward, easy-to-understand, and brightly illustrated book would make a good addition to any nonfiction collection looking to fill biology gaps.--Clara Hendricks

Wells introduces young readers to a complicated topic: human DNA. He explains the concept of living things and describes the cells that compose them and the DNA molecules that control the chemical instructions for making new body parts. He details DNA's structure (a twisted ladder), its component molecules (adenine, guanine, thymine, and cytosine), and the genes on chromosomes where DNA is found. Contending that all human DNA is 99 percent identical, he touches on the ways that traits are expressed in individuals. Corrigan's cartoon illustrations are colorful and appealing. The artwork includes some scientific diagrams, although most depict visual metaphors, such as a DNA factory that produces a variety of cells for skin, bones, muscles, and blood. Overall, an accessible introduction to a complex topic; part of the Tell Me Why series (2 titles).