Scientists say pea-size organoids of human brain tissue may offer a way to study the biological beginnings of a wide range of brain conditions, including autism, bipolar disorder and schizophrenia. Alysson Muotri/UC San Diego Health Sciences hide caption
The sex that a turtle develops into is determined by the temperature that an embryo experiences when it's inside the egg. Ye et. al / Current Biology hide caption
In these two two-cell mouse embryos, the surface of the embryos is outlined in orange, the DNA in the nucleus is indicated in blue and the activity of the LINE-1 gene is indicated via bright red spots. Ramalho-Santos lab/UCSF hide caption
This sequence of images shows the development of embryos formed after eggs were injected with both CRISPR, a gene-editing tool, and sperm from a donor with a genetic mutation known to cause cardiomyopathy. OHSU hide caption
