The video component of the Third International Mathematics and Science Study (TIMSS) has documented that U.S. students spend most of their time in the mathematics classroom practicing routine procedures as opposed to inventing, analyzing, and proving them. The challenge for preservice and inservice teachers lies in creating a classroom environment where both procedural and conceptual understanding on the part of young students is encouraged and modeled so that the "whys" are no longer ignored and left unanswered. In this article, the authors investigate preservice teachers' understanding of the area of a parallelogram. (Contains 5 figures.)