Cloud Activation (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption Cloud droplets form when the amount of water vapor reaches a threshold value. Larger cloud droplets form when organic molecules (in red) are present on the surface instead of dissolving in the interior, or bulk, of the droplet. Credit James Davies, Berkeley Lab Usage Restrictions Editorial use only. Commercial use prohibited. 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.