The purpose of this protocol is to understand the propensity of nanomaterials to induce oxidative stress in the mitochondria. Induction of the oxidative stress is a common toxicity associated with nanoparticles. Generation of reactive oxygen species (ROS) and its control by antioxidant systems is a part of normal cellular metabolism. The total oxidative stress generated in a cell is the result of combined oxidative stress from various organelles such as endoplasmic reticulum, lysosomes, mitochondria, and peroxisomes. D isturbance of redox homeostasis and accumulation of ROS damages cellular organelles and DNA, eventually leading to cell death. Another consequence of excessive ROS generation is activation of stress-related pathways and release of pro-inflammatory cytokines. Depending on the source of ROS, organelle-specific toxicity can also contribute to stress response.