Zebrafish are small freshwater fish native to the rivers of South Asia. They are popular in scientific research due to their transparent embryos, which allow scientists to observe development in real-time. Zebrafish typically grow to about 2 to 4 centimeters in length and are known for their distinctive horizontal blue and silver stripes. These fish are often used in studies related to genetics, development, and disease, making them valuable in fields like biomedical research. Their rapid reproduction and ease of care in laboratory settings further contribute to their popularity among researchers.