An Artistically Colored Electron-Microscopic Image of a Porphyromonas Gingivalis Cell (image) Okinawa Institute of Science and Technology (OIST) Graduate University Share Print E-Mail Caption Most bacterial cells are covered in tiny, hair-like structures called pili. Their diameter is smaller than 1/10,000th of a human hair. Credit S. Shibata, OIST Usage Restrictions Credit given Share Print E-Mail 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.