Passive cooling (IMAGE) Massachusetts Institute of Technology Caption MIT researchers have developed a two-layer passive cooling system, made of hydrogel and aerogel, that can keep foods and pharmaceuticals cool for days without the need for electricity. In this photo showing a close-up of the two-layer material, the upper layer consists of aerogel and the bottom layer of hydrogel. Credit Courtesy of Jeffrey Grossman, et. al Usage Restrictions Images are made available to non-commercial entities, press and the general public under a Creative Commons Attribution Non-Commercial No Derivatives license. You may not alter the images provided, other than to crop them to size. A credit line must be used when reproducing images. 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.