Embryonic stem cells are special cells derived from early-stage embryos, typically around 3 to 5 days old. These cells have the unique ability to develop into any type of cell in the body, making them essential for research and potential medical treatments. They are often studied for their role in understanding human development and disease. Researchers are particularly interested in embryonic stem cells because they can help in regenerative medicine, which aims to repair or replace damaged tissues and organs. However, their use raises ethical questions, as obtaining these cells involves the destruction of embryos.