One should not think that because zebrafish (Danio rerio) are fish, they are somehow inferior to any species of mammal. They certainly aren't. Zebrafish are small schooling cyprinids, getting their name from the adults' prominent black and white stripes. Native to the Indian subcontinent, these laterally compressed organisms are widely distributed in slow-moving streams and stagnant habitats. Where they exist, zebrafish are typically the most abundant species (McClure, et al., 2006, p. 562). They also have a short generation time which allows for the hatching of large numbers in a short period of time. The species has become popular among enthusiasts due to its hardiness, cold resistance and ease of breeding. Over the years, selective breeding has created numerous different strains. Zebrafish are best known for their transparency, their short growth cycle and their high ability to regenerate. Although regeneration occurs at a rather low rate in mammals, this regenerative capacity is unfortunately powerless and does not sufficiently restore damaged tissue. Once mature, they lose the ability to replenish cells at the sites of injury. In contrast, zebrafish are able to retain the ability to regenerate throughout their adult life. Zebrafish are highly regenerative animals with the ability to heal injuries to the heart, retina and other tissues. In an experiment conducted by Azevedo et al. (2011, p. 1), the regeneration capacity of zebrafish was studied using a designed experiment in which the fish's fin was repeatedly amputated. The goal of this particular study was to determine whether fin regeneration is limited. This experiment was designed to study the effect that recurrent fin amputations and experience...... middle of paper...... Scientists have found that hearts regrow without scarring following injury. They found that regeneration in the zebrafish heart is not driven by stem cells but rather by the proliferation of existing cardiomyocytes (heart muscle cells). They also point out that the exhibition of this regenerative response could be due to enlargement of the heart via hypertrophy or hyperplasia. While the results of these experiments do not suggest the zebrafish's ability to regenerate from a single stem cell, they do indicate that the animals rely on their limitless regenerative capacity to heal after injury. The fact that they can quickly regrow body parts by scaring shows just how intriguing these little organisms are. The mechanisms involved in zebrafish regeneration have provided insights into human biological processes, due to its genetic similarity to humans.