I developed a new zebrafish laboratory module to introduce undergraduate cell biology students to animal handling, microscopic image acquisition, and analysis. This laboratory module addresses several of the core competencies outlined by the Partnership in Undergraduate Life Science Education Vision and Change in Undergraduate Biology Education, including integration of quantitative reasoning, the process of science, and modeling and simulation. Students work with two or more strains of zebrafish to compare pigmentation in the caudal fin. Adult zebrafish are anesthetized and the caudal fin is amputated. Melanophores, which are the melanin-containing pigmented skin cells, are then imaged in the caudal fin via microscopy. Students analyze their acquired images on the computer using the freeware FIJI (Fiji Is Just ImageJ, NIH) to calculate the area of pigment dispersal (an estimate of cell size) and total pigmentation in the caudal fin. These measurements are compiled as class data and are compared across multiple lines of zebrafish to allow students the opportunity to work with authentic datasets. Students in this lab are excited to work with zebrafish and gain a deeper understanding of model organism research. This lab module is ideal for the undergraduate setting in that it provides students with an opportunity to design and perform a novel experiment, it uses limited resources, can be completed in as few as two lab sessions, and can be performed with many lines of zebrafish.