The old adage that a picture is worth a thousand words also holds true in cell biology. Much of the knowledge that we have of the structures and functions of cells has been acquired by biologists peering through the eyepieces of microscopes. The point of this lesson is to provide an opportunity for students to observe cell biological data while practicing the critical skills of careful observation and scientific questioning. In this exercise, designed for use in the middle or high school classroom, students measure changes in the nuclear/cytoplasmic ratio (N/C ratio) during the early stages of development of the sea urchin embryo. The N/C ratio is an important concept in understanding the early development of embryos when the number of cells increases without increasing the volume of the embryo. This lesson, which does not require the use of microscopes, integrates biology and mathematics, helps students develop the ability to ask scientific questions, and provides a model for the integration of highly detailed images of cells into middle and high school classroom instruction in cell biology. (Contains 5 figures.)