Humans are daily exposed to a wide variety of xenobiotic electrophiles through living environments, lifestyles, and dietary habits. Electrophiles have low electron deficiency sites in the molecule that are able to covalently bind with nucleophiles such as cysteine residues of proteins to form adducts. It has long been believed that this is the cause of the toxicity. For example, acetaminophen itself exhibits little electrophilicity, but its electrophilic metabolite produced by metabolic activation forms protein adduct associated with liver injury. On the other hand, the discoveries of endogenous electrophiles in the body and cellular redox signaling pathways activated by covalent modification of sensor proteins with reactive thiols suggested possibility of the existence of defense systems against exogenous electrophiles. We found that exposure of cells to exogenous electrophiles with different structures at low dose causes the activation of a variety of redox signaling pathways associated with an adaptive response. We also showed that exogenous electrophiles undergo capturing by reactive sulfur species, leading to formation of sulfur adducts, thereby repressing reactivity of exogenous electrophiles. In this symposium, I also introduce the importance of electrophile as priority a component in the "exposome" research.