Not only is it an incredible spectacle, highlighting the moment a new life begins, but the size of the flash may determine the quality of the fertilized egg.
An explosion of zinc fireworks occurs when a sperm enzyme activates the human egg. Scientists at the university had witnessed these sparks in mice five years ago and just recently were able to witness the same spark of life happen in human eggs, and released a report and video showing the fantastic discovery.
The flash of light was brighter in some of the eggs than others, which Woodruff and the other study authors think indicates a healthier egg, since zinc is a major factor in the catalyst of growth and change into a new organism.
The discovery could help fertility doctors pick the best fertilised eggs to transfer during in vitro fertilisation (IVF).
Scientists had seen the phenomenon occur in other animals but it is the first time it has been shown in humans.
The study was published April 26 in Scientific Reports. As the zinc shoots out, it binds to small molecules which emit a fluorescence which can be picked up by camera microscopes.
And what's more, researchers found different sizes of light and said the size can actually reveal the quality of the egg that's being fertilized, the Telegraph reported.
"There are no tools now available that tell us if it's a good quality egg", she said.
Duncan was an assistant research professor in obstetrics and gynecology at Feinberg when she made the discovery and will become the executive director of Northwestern's Center for Reproductive Science on August 1.
"Often we don't know whether the egg or embryo is truly viable until we see if a pregnancy ensues", Feinberg said on Northwestern's website.
Dr. Feinberg continued by saying, "That's the reason this is so transformative".
When the romantic sparks fly, zinc sparks sometimes fly, too.
It took them a few years to figure out how to image this event, but by 2014, they'd managed to film the event for the first time ever, and watched as billions of zinc atoms were released at the exact moment when a mammal's egg is pierced by a sperm cell.
Using only the most viable embryos could save a lot of time and heartache for IVF patients, while sparing them from the potential risks of extended embryo culture (keeping the embryo in a culture medium from the third day of fertilization on, which has been associated with pre-term births) and multiple embryo transfer (which increases the risk of becoming pregnant with multiple fetuses), the study says.
The paper is titled "The Zinc Spark is an Inorganic Signature of Human Egg Activation".
This discovery was made by Zhang, a postdoctoral fellow at Northwestern.
The research was supported by the Thomas J. Watkins Endowment and a research grant from Ferring Pharmaceuticals and the W.M. Keck Foundation.