Human Embryonic Stem Cells (IMAGE) University of California - Riverside Caption The top image shows a control colony of human embryonic stem cells at 48 hours. The bottom image shows, also at 48 hours, a colony of human embryonic stem cells treated to sidestream smoke from a harm reduction brand (the colony has been killed by the smoke treatment). Credit Talbot lab, UC Riverside. Usage Restrictions None 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.