This strange creature is a day-old zebrafish embryo, just two millimetres long. On the left is the head – the darker circle will become its eye, while the transparent shape just above it to the left is the developing brain. The long tail to the right will become the muscles it uses to wriggle and swim, and it's perched on a large sac of yolk providing food as it grows. But although it may look nothing like a human embryo, we have many features in common. One example is neural crest cells – these are special cells that form just behind the brain, then spread out across the whole body to form cartilage, bone, nerve cells and much more. Scientists are studying how neural crest cells form and move in these little fish to get clues as to how human babies develop and grow, and what happens when things go wrong.
Written by Kat Arney
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.