Silica Microspheres (IMAGE) University of California - San Diego Caption A scanning electron micrograph of porous silica microspheres filled with perfluoropentane vapor. This new material, invented at the University of California -- San Diego, is visible with Doppler ultrasound, sticks to breast tissue and can mark the location of tumors too small to be seen or felt during surgery. Credit Paul Martinez, UCSD Usage Restrictions Permission granted to use this image to illustrate stories about the new material reported here. For other uses, please send a request to firstname.lastname@example.org 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.