Danio rerio, commonly known as the zebrafish, is a small freshwater fish native to the rivers of South Asia. It typically grows to about 2.5 to 4 centimeters in length and is recognized for its distinctive horizontal blue and silver stripes. Zebrafish are popular in aquariums and are often used in scientific research due to their transparent embryos and rapid development. These fish are social creatures that thrive in groups and prefer to inhabit shallow waters with plenty of vegetation. Danio rerio is also known for its resilience and adaptability to various environmental conditions, making it a valuable model organism in studies related to genetics, development, and disease.