Researchers in California are attempting to make an artificial testicle that will produce human sperm.

Dr. Paul Turek, director of the Turek Clinic in San Francisco, which specializes in male infertility, said the goal is not to create a testicular implant for men, but a "sperm-making biological machine" that will help scientists learn more about just what causes male infertility.

"We're trying to recreate the process of sperm production in a three-dimensional system," Turek said. "Simple laboratory conditions can't get it done in humans. Our concept is to actually recreate the testicle itself."

Turek and his team will build the faux testicle by first growing cells that nurture sperm in the lab and then adding a man's stem cells to hopefully create new sperm cells. Turek said the "holy grail" of his research will be to produce sperm for infertile men that could be used in IVF treatments to conceive children, but achieving that goal will likely not happen for many years.

Dr. Rick Paulson, director of the fertility program at the University of Southern California , told ABC News that if Turek and his team are successful, it could be an exciting step forward for men who lose their testicles to cancer, accidents or other factors that leave them without the ability to make sperm.

But the team will face a few hurdles, Paulson said.

"The processing of DNA is very complicated to go from a regular cell to a germ cell" like sperm, which have half the number of chromosomes as other cells in the body, Paulson said. "Not only do you have to split the chromosomes in half, but you also have to package the DNA in a very specific way. I think it will be quite challenging."

Approximately 15 percent of couples are infertile, and in about half of those cases, the man is the source of the infertility, according to the Mayo Clinic. Scientists are already able to harvest sperm from the testicles of men who produce their own sperm, just not enough to be fertile.

Paulson said the next, far more challenging task for researchers will be to create eggs from stem cells to help infertile women.