Talk about fireworks in the bedroom.

When a sperm cell fuses with an egg, it triggers the sudden release of zinc atoms from the egg's surface. That's been known since 2011. Now, for the first time ever, scientists have observed these "sparks" in action (see video above) and figured out where they come from.

“The egg first has to stockpile zinc and then must release some of the zinc to successfully navigate maturation, fertilization and the start of embryogenesis,” Dr. Thomas V. O’Halloran, a professor of chemistry and molecular biosciences at Northwestern University in Chicago and one of the scientists, said in a written statement. “But exactly how much zinc is involved in this remarkable process and where is it in the cell? We needed data to better understand the molecular mechanisms at work as an egg becomes a new organism.”

For the study, the researchers used a set of new imaging techniques to count and map the positions of individual zinc atoms in mouse eggs. They discovered that every egg has about 8,000 tiny compartments called vesicles, each containing about one million zinc atoms. The compartments release their contents simultaneously when the egg is fertilized.

“Each egg has four or five of these periodic sparks," O'Halloran said in the statement. "It is beautiful to see, orchestrated much like a symphony. We knew zinc was released by the egg in huge amounts, but we had no idea how the egg did this.”

And beauty is only part of the equation. According to the researchers, the new imaging techniques may prove beneficial for in vitro fertilization--by helping fertility doctors identify human eggs that are most likely to yield healthy embryos.

“If we can identify the best eggs, fewer embryos would need to be transferred during fertility treatments," study co-author Dr. Teresa K. Woodruff, an expert in ovarian biology at the university, said in the statement. "Our findings will help move us toward this goal.”