Immortalized cells, engineered to bypass senescence, are essential for controlled laboratory research, while cancer cells arise from genetic mutations and exhibit uncontrolled proliferation, aiding in cancer biology studies. Their applications span drug discovery, disease modeling, and therapy testing, though both face ethical and practical challenges. Innovations like organoids and CRISPR are transforming cellular research. Additionally, early identification of autism symptoms in toddlers enables timely intervention for better developmental outcomes.