What unique physical feature of early-stage zebrafish embryos allows real-time observation of internal organ development?

Transparency

A defining physical advantage of the zebrafish model lies in the transparency of its embryos during the initial few days of life. This clarity is extraordinarily useful because it provides scientists with a non-invasive window into the developing internal structures. Researchers can directly observe processes such as the formation and beating of the heart, the development of the brain, and the growth of blood vessels in real-time. This ability to visualize these critical organs developing without needing invasive procedures is a major differentiator compared to models where development occurs internally, such as mammals.