The egg before fertilization (IMAGE) European Synchrotron Radiation Facility Caption Artistic depiction of how fusion of a sperm with an egg at fertilization triggers a cascade of events that ultimately zips up the filamentous matrix around the egg, thus permanently blocking polyspermy. Credits: Marcel Bokhove Credit Marcel Bokhove Usage Restrictions Mention of the credit 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.