Not only is it an incredible spectacle, highlighting the very moment that a new life begins, the size of the flash can be used to determine the quality of the fertilised egg.
Researchers from Northwestern University, in Chicago, noticed that some of the eggs burn brighter than others, showing that they are more likely to produce a healthy baby.
Over the last six years this team has shown that zinc controls the decision to grow and change into a completely new genetic organism.
In the experiment, scientists use sperm enzyme rather than actual sperm to show what happens at the moment of conception.
“These fluorescence microscopy studies establish that the zinc spark occurs in human egg biology, and that can be observed outside of the cell,” said Professor Tom O’Halloran, a co-senior author.
In a companion paper published in Scientific Reports on March 18, a zinc spark is shown at the precise time a sperm enters a mouse egg.
This discovery was made by Nan Zhang, a postdoctoral fellow at Northwestern. Little is known about the events that occur at the time of fertilization, because it is difficult to capture the precise time of sperm entry.