Kari Seitz is one of just two female FIFA referees from the United States and has officiated the highest level of women's soccer, including last month's World Cup.
Seitz refereed the third-place game between France and Sweden, the top match a U.S. official could work in the tournament since the American team was in the final.
But Seitz, 40, said she would not be as good a referee if she hadn't worked both men's and women's soccer.
She has been a FIFA referee for 12 years and believes she is the only person -- male or female -- to officiate four World Cups. She also has worked two Olympic women's tournaments.
As for men's experience, Seitz was a referee and assistant referee in Major League Soccer from 1998 to 2001 and currently works some college and amateur men's games near her hometown of San Mateo, Calif.
Her theory: To reach your potential, you need to have as much accumulated experience as possible with both the men's and women's games, along with a variety of skill levels, nations and ethnicities.
Men need to work women's games. Women need to work men's games.
"It's a craft," she said. "If you just did women's or just men's football, you wouldn't be the best referee you can be."
It helps to have a thick skin and a sense of justice.
"I have a natural inclination for making things fair," Seitz said.
In addition -- and this may surprise fans accustomed to dour officials -- most men and women referees at the top have a high level of education and a good sense of humor, said Sandy Hunt, one of the first two women to referee in MLS, in 1998.
Take Bibiana Steinhaus, a German referee who officiated the Women's World Cup final between the U.S. and Japan. In 2007, she became the first woman elevated to referee men's Level 2 matches in Germany's famed Bundesliga.
In her first live TV men's match last year, a player inadvertently patted her breast. Both dissolved into laughter.
"She was standing a bit further away than I thought -- I meant to give her a pat on the back," defender Peter Niemeyer told reporters afterward. "But you do have to entertain the fans a bit, too."
About 400 women worldwide are certified FIFA referees, approximately one-fifth of all referees from 208 FIFA-member nations. For some time, women have officiated soccer at the highest levels in the women's game -- Olympics and World Cup. No women have refereed in the men's Olympics or World Cup, where religious restrictions in Islamic countries make that possibility an unlikely one.
So far, women's advances in men's soccer have been limited to the lower tiers of the game.
In 2004, for instance, a woman officiated a men's World Cup qualifier. In June of this year, an all-women's crew worked a men's second-tier pro match in Czech Republic, a first for the men's game.
In the United States, women's highest-profile assignments in men's soccer came 13 years ago during Hunt's time with MLS. No women currently referee MLS games.
Part of the reason is that a women's pro league now exists, which satisfies FIFA's requirement that, in order to be eligible for international assignments, officials must first prove themselves at the highest domestic level. In Hunt's era, MLS was the only route to the bigs.
Now women have many options and help getting there. In January of this year, U.S. soccer hired Sandra Serafini as the Women's Professional Referee Coordinator. She will oversee development of female officials in the United States, including being responsible for assigning officials to WPS games and making contact with female FIFA referees.
Serafina also will work with the U.S. director of pro referees to assign female officials to semi-pro men's games in the MLS preseason and reserve leagues, NASL and USL Pro.
Getting certified as a referee means first taking a class and passing the test, then working up the ladder. Most people start at Grade 8 and advance through game experience, assessments, fitness testing and number of games worked. In the U.S., the highest level, a national referee, is Grade 3. Grade 1 is an international referee. To become an international referee, your name must be submitted by your federation and accepted by FIFA.
Outside of some premier men's leagues in Europe, few men or women make a living from refereeing, even if they have reached the top of their profession. Steinhaus is a German police officer. Seitz squeezes in match assignments with full-time work as general manager of two advertising agencies at OMD, one of the world's most prominent media agencies. Just about all her vacation time is taken up by officiating in a job that pays relatively little -- "a tax write-off," Seitz said.
She was married for 17 years before she and her husband took a two-week, non-work trip together in 2009.
"Luckily, he's very understanding," Seitz said.
For both men and women officials, soccer likely has the most rigorous physical standards of all top-level sports.
Two of three officials -- the assistant referees -- are limited to the sideline on one-half of the field, at least 100 yards long and 50 yards wide. The head referee patrols the rest of it.
Accordingly, FIFA referees are required to demonstrate a remarkable level of aerobic fitness, and they are also forced to retire at age 45.
Part of their test consists of running 12 laps around a 400-meter track. The laps consist of intervals: 150-meter sprints followed by 50-meter recovery walks.
Men get 30 seconds to complete each sprint and 35 seconds for each walk. Women get 35 and 40.
This comes after six 40-meter sprints with 90 seconds of rest in between. Men must take no longer than 6.2 seconds on each sprint, women no more than 6.6 seconds.
"Had I known how much running would be involved, I probably would've picked beach volleyball," jokes Seitz, who devotes about eight hours a week to physical training (running and weightlifting).
Hunt, 52, retired as a FIFA referee in 2004. She's now a FIFA assessor and instructor for men and women, as well as evaluating and assigning matches for the Pac-12 women and West Coast Conference men and women.
While soccer is one of the rare sports where rules and equipment are the same for both sexes, both Hunt and Seitz say officiating them is different.
As far as the game itself, women have less power but more precision, said Hunt, with more short passes.
Men's games are faster with more "hot spots" -- places where tensions are running high at various places on the field simultaneously. Body language is different.
"Men do crazy-weird stuff you don't see in a women's game," Seitz said. "Believe it or not, they're very, very emotional."
Men and women will disagree with the referee the same amount, but express it differently -- men might gather, eyes bulging and get in your face, Hunt said. Women will approach you privately or say something, but it's not so aggressive.
"Won't disagree less, but they're less disagreeable," Hunt said.
If a guy wants to exact revenge on a player who fouled him or a teammate, chances are he will do it right away and might even share beers afterward. Not women.
"She'll make sure there's justice," Hunt said. "[Women are] willing to wait a couple seasons. Girls think about it on the bus ride, they talk about it."
Seitz is 5-foot-4. Part of the challenge for her is when two players argue, literally, over her head, it is hard to defuse the situation.
Hunt said women referees can't get physical.
"I'm not a threat to any man," Hunt said. "I'm not going nose-to-nose with some big soccer star and try to overpower him because it would be foolish and look ridiculous. My strategy is to try to gain cooperation."
Hunt said her career in a men's game would not have been possible had established male referees not helped her along the way, especially at the beginning. She feels an obligation to do the same with women coming up.
"When you're the only one doing it, you're holding the door open for the other women who want a chance," she said. "All I want to do is advance the ball. I don't feel like I need to score a goal. If I can just keep my foot in the door and do a solid job, people -- men or women, maybe of color, minorities or whatever -- should get just as fair a chance."