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 in regenerative medicine and developmental biology. Scientists study embryonic stem cells to understand how cells differentiate and to explore potential treatments for various diseases. However, their use raises ethical concerns, as obtaining these cells involves the destruction of the embryo, leading to ongoing debates about the moral implications of stem cell research.