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This isn’t your typical Fourth of July display — when a human egg is fertilized by sperm, there’s a big explosion of zinc “fireworks.”

The beautiful burst could hold clues to making in vitro fertilization more successful, according to a study published Tuesday in Scientific Reports. The brighter the fireworks, the more viable the fertilized egg appeared to be.


The researchers fertilized eggs with a sperm enzyme for the sake of the experiment, because full fertilization of a human egg isn’t permitted for scientific research in the US. Specifically, they were looking at the eruption of zinc, which plays an important role in the development of an embryo. To visualize the zinc, researchers added small molecule probes that fluoresced under certain lighting.

The researchers hope that by monitoring the fireworks at the time of fertilization, they’ll be able to pinpoint the best eggs to transfer to a woman’s uterus during IVF to maximize the odds of success.