We have developed an upper-level undergraduate laboratory exercise that enables students to replicate a key experiment in developmental biology. In this exercise, students have the opportunity to observe live chick embryos and stain the apical ectodermal ridge, a key tissue required for development of the vertebrate limb. Impressively, every student who has tried this protocol has been successful, making it a good introduction to the use of the chick model system in studying development. The array of materials about limb development, using chick embryos in teaching laboratories, and the history of this experiment provide a rich background for teachers and students.