Salk Science Image (IMAGE) Salk Institute Caption Pictured are blastocyst-like structures (blastoids) from cultured mouse cells immunofluorescently stained for the trophectoderm marker CDX2 (green) and the inner cell mass marker SOX2 (red). The trophoectoderm is the term for the outer cells of the blastoid. Credit Salk Institute/Waitt Advanced Biophotonics Core Facility Usage Restrictions with credit and related coverage. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.