Why is the use of letters in algebraic expressions and equations--variables--the source of such uncertainty for students and teachers? The authors studied a sixth-grade classroom and observed that students hold many misconceptions about variables. Some students hold an algebraic view of the equal sign. For them, it indicates an equation and signals them to solve for an unknown variable. Others view it only as a signal to compute. As the authors battled their own frustrations with students' misconceptions about variables, they discovered that their meanings for variables could be further sorted into groups and that those meanings changed over time. They also found that certain problem contexts and teacher questions could help shift students' meanings of variable. In this article, the authors share their findings and some productive ways to work with students' natural ways of thinking.