Hox genes specify identities mainly in the anteroposterior axis in various animal tissues, some of them forming part of the internal organs and systems. The expression and activity of these genes have been analyzed mainly in Drosophila melanogaster, the fruit fly, and in mouse; in the former, the functional study of Hox genes has been detailed predominantly in epidermal structures, but their role in internal organs poses some challenges, particularly in pupae. One of these genes, Abdominal-B, dictates the development of many internal organs in the posterior abdomen of the fly, yet techniques for its analysis, like in vivo time-lapse, have long been impractical. The protocol outlined in this chapter presents a simple and effective method that not only addresses this issue but also opens up new approaches to previously inaccessible in vivo developmental questions, such as the spatial challenges of abdominal organ packing and the minimal requirements for the coordinated growth of organs.