This handbook presents a compilation of plant histopathology laboratory practices and microscopy techniques for study plant tissues under biotic stress. It will serve as an easy-to-reference material for professors, undergraduate and graduate students and researchers from different areas who work with the interaction between plants and pathogens, whether they are fungi, viruses or bacteria. Besides, it will also help unveil the structural, ultrastructural and histochemical changes induced by plants when challenged by plant pathogens.