It is an incredible moment: doctors taking out a kidney in order to share it with someone else. But to get there, you have to make a match. So, what does it take to get an organ donation match?

"It's an elaborate process," said Dr. Erik Finger, a kidney transplant surgeon with university of Minisota Fairview.

Finger was part of a team that just executed a chain of five kidney transplants, which required 10 operations at three different hospitals. They had to go to such a wide group, because of a number of willing donors who were not matches for their friends.

"Blood typing is the most important thing, where you have pre-formed antibodies against a particular blood type," said Finger.

Lung, heart, liver, kidney: if the blood types don't match a transplant is not going to happen.

With the heart, size also matters, according to Susan Mau Larson of LifeSource, a Twin Cities company that handles coordination between donation and transportation.

She said the body can't handle a too big or too small heart.

Each organ has a different degree of sensitivity to rejection, according to Finger, but "the hardest organ is the kidney because we look for specific details about the degree of matching."

For the kidney, doctors look into your genetics. They take a blood draw to analyze the human leukocyte antigen (HLA) molecules.

"These are the proteins involved in immune response. Against all foreign proteins. Infections, bacteria infections. The system the body has is different between different people," said Finger.

Prior blood transfusions, transplants or pregnancies make the body pickier about a kidney match.

"We look at the six most important molecules, the six most likely to cause an immune response, and we say, 'Of those how many of those are in common,'" according to Finger.

Timing and geography also matters. You can only keep a lung or heart on ice for six hours. And as researchers invent new anti-rejection drugs, they won't need a perfect match. Pretty soon, "good-enough" might do.

"We know there's potential to do better," said Finger.