The objective of this teaching note is to generate a laboratory exercise, which allows students to get a hands-on experience of a cell biology technique. The short duration of the laboratory classes is the biggest challenge with the development of a cell biology lab for an undergraduate curriculum. Therefore, it is necessary to design a laboratory exercise that enables the students to carry out cell biological assays in the desired time. This laboratory exercise focuses on tracking protein expression levels along a spatial (space) and temporal (time) axis in developing Drosophila melanogaster organ primordium. Here we use the protein trap model developed in Drosophila to demonstrate the sub-cellular localization of proteins. The protein trap transgenic flies have green fluorescent protein (GFP) reporter tags to the full-length endogenous proteins that allow observation of their cellular as well as sub-cellular distribution. Since the life cycle of Drosophila is short, it is easy to rear them in the lab and also use them as an excellent model for an undergraduate lab curriculum. The goal of this exercise is to train undergraduate students and teach them the use of one such powerful tool which enables the localization of proteins.