In this chapter, we will describe two different techniques used to trace storage and mobilization of intracellular granule-derived mediator proteins in eosinophils. The first is confocal laser scanning microscopy (CLSM) used to investigate immunofluorescence labeling in cytospins, and the second is subcellular fractionation, leading to the generation of fractions that may be analyzed for their organelle elution profiles using appropriate protein, enzyme, and organelle marker assays.