Learning through meaningful problem solving is integral in any successful mathematics program (Carpenter et al. 1999). The National Council of Teachers of Mathematics (NCTM) promotes the use of problem solving as a means to deepen understanding of all content areas within mathematics (NCTM 2000). This article describes a first-grade lesson that uses the multifaceted problem of measuring a puddle to explore students' conceptions and prior knowledge of measurement, measurement tools, and relationships among the measurement attributes. The goals addressed in this investigation include assessing initial understanding of measurement. More specifically, the authors sought to determine the measurable attributes of a puddle that students identified, and which units and processes of measurement they recognized. (Contains 4 figures.)