You probably learned in high school health class that when a sperm and an egg get together, they fuse into an embryo - the early stages of a baby.  But what you didn't learn was why and how that sperm and egg found each other in the first place.  And that's because until recently, researchers did not know.  

In 2005, Japanese researchers identified a protein in the sperm that could recognize the egg.  They named the receptor protein “Izumo,” after a Japanese marriage shrine.  But they still did not know what the counterpart was on the egg side of the equation.  Until now.

A team of British researchers reported in the latest issue of Nature that they have located the protein receptor on the egg that can identify sperm.  They named it “Juno,” after the Roman goddess of fertility.

The team of researchers from the Wellcome Trust Sanger Institute reported on their website that they developed mice that “lacked the Juno protein on the surface of their eggs,” and found them to be infertile. In other words, these Juno-less eggs could not fuse with normal sperm.  This is similar to the studies that identified Izumo as the protein receptor on sperm.

This finding completes the puzzle of conception and could help couples undergoing IVF - or in vitro fertilization - see greater success with the procedure.  And it could also help women who suffer from infertility identify the cause of their condition.

Here's more on the research in this video: