On-Demand Vaccines (image) University of Washington Caption This image shows a collection of vaccinating nanoparticles, which at their largest are about 1,000 times smaller than a human hair. The inset graphic is a representation of how the engineered proteins decorate a nanoparticle's surface. Credit University of Washington Usage Restrictions Photo credit required. 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.