Introducing sophisticated mathematical ideas like fractals and infinity, these hands-on activity books present concepts to children using interactive and comprehensible methods. With intriguing projects that cover a wide range of math content and skills, these are ideal resources for elementary school mathematics enrichment programs, regular classroom instruction, and home-school programs. Reproducible activity sheets lead students through a process of engaged inquiry with plenty of helpful tips along the way. A list of useful terms specific to each activity encourages teachers and parents to introduce students to the vocabulary of math.  Projects in this first of the two Big Ideas books include “Straw Structures,” where children get hands-on experience with measurement and 3-D visualization; “Kaleidoscopes,” in which students use geometry to build a mathematical toy; and “Crawling Around the Möbius Strip,” where kids build a physical example of infinity.