Lysosomes are membrane-bound organelles important for various cellular processes. They contain hydrolytic enzymes utilized in the metabolism of some biomolecules. The extracellular cargo (e.g. nutrients, toxins) binds to the cell membrane and is subsequently transported into membrane-bound endosomes for further degradation by lysosomes while intracellular components are transported to lysosomes through autophagy. Lysosomal dysfunction is associated with many human conditions such as aging and neurodegenerative disease. BioVision has developed the Lysosomal Cytotoxicity Dual Staining Kit (cell-based) which contains two probes; membrane permeable, selective Lysosomal Stain and Cell Death Marker. We also include a Positive Control Reagent, which increases lysosome activity and staining, thus serves as an experimental control. This easy-to-use, non-radioactive kit allows studying the regulation of lysosome and cytotoxicity at the cellular level by using Fluorescence Microscopy and Flow Cytometry in cultured cells.