Toxic substances and environmental contaminants can significantly affect cellular homeostasis, hormonal signaling, and immune mechanisms. The results of in vitro analyses allow toxicologists to predict health risks, identify possible mechanisms of action, and support regulatory decision-making regarding chemical safety and individual health protection. This practical handbook provides an overview of modern experimental approaches used to evaluate the effects of toxicants, environmental pollutants, and endocrine disruptors on animal and human cell models. It focuses on procedures that enable monitoring of changes in cellular function, metabolism, gene expression, and overall cell health, thereby contributing to a deeper understanding of how individual exposure impacts human health.