Image analysis is a critical part of IHC and IF experiments because reliable conclusions depend on measuring staining accurately and consistently. In this video, we introduce ImageJ/FIJI for IHC and IF image analysis, including image types, basic processing steps, intensity measurement, area fraction analysis, thresholding, and adaptive thresholding methods. We also explain how these approaches can help researchers generate more meaningful and reproducible data from fluorescence and immunohistochemistry images.