The chick or baby chicken is not only a favorite as a reminder of spring and as a live Easter gift for children in the United States, but is also well studied by embryologists, toxicologists, and histologists. Because of their relatively low cost, abundance, and year-round supply, chicken embryos make ideal laboratory organisms. The digital image presented below illustrates a darkfield microscopy view of a 96-hour chicken embryo.

View a chicken embryo that is 72 hours old.

View a chicken embryo that is 80 hours old.

Chicken embryos and cells grown in the laboratory may reduce animal testing by replacing exposure trials on mice and rats. In the field of genetic engineering, state-of-the-art research on gene function is being carried out on cultured chicken cells instead of engineered mice. Most chicken genes have equivalents in humans, therefore, utilizing chicken cells to identify the proteins for which genes code, and their locations on the chromosomes has a direct impact on understanding human biology.

Chicken embryos develop in eggs rather than inside the mother, as in mice and rats, making the control of experiments much easier for research scientists utilizing the chicken. Since 1967, when killed measles virus-derived vaccines were abandoned because of severe reactions in some children, measles vaccines are produced by weakening the live virus through transplantation from 40 times to 85 times into chicken embryos. Similarly, a stronger mumps vaccine was developed by passing the virus repeatedly through hens' eggs and chicken embryos.