Embyronic Cell (image) Rockefeller University Share Print E-Mail Caption Forty-two hours after they began to differentiate, embryonic cells are clearly segregating into endoderm (red), mesoderm (blue) and ectoderm (black). Researchers say the key to achieving this patterning in culture is confining the colonies geometrically. Credit Brivanlou Lab, The Rockefeller University Usage Restrictions None Share Print E-Mail 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.