Nanotubes (IMAGE) Johns Hopkins University Caption Tubes, visible as the light green lines, are roughly seven nanometers in diameter — about two million times smaller than an ant — and several microns long, or about the length of a dust particle. Credit Johns Hopkins University Usage Restrictions None License Original 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.