Serena Williams wrote a powerful open letter to girls and women everywhere.

One of the greatest athletes of all-time, superstar Serena Williams gets it done on and off the court.

In addition to being a 22-time Grand Slam singles champion, the tennis legend has pushed back against body-shamers, shut down rude reporters, spoken out against police violence, and just recently teamed up with her sister, Venus, to open a center for gun violence victims in their hometown of Compton.

But that's not all she's done lately.

In an open letter addressed to "incredible women who strive for excellence," Williams shared some real talk about the real effects of gender bias.

Appearing in Porter Magazine's "Incredible Women of 2016" issue (and reprinted at The Guardian), Williams talks about what it's like being one of the most hugely successful women in the world and the struggle and frustration that goes along with it.

Opening with a line about her childhood dream of becoming the greatest tennis player in the world, Williams went on to say how thankful she is to have a family that was there for her to support that goal.

"People call me one of the 'world’s greatest female athletes,'" she writes. "Do they say LeBron is one of the world’s best male athletes? Is Tiger? Federer? Why not? They are certainly not female. We should never let this go unchallenged."

Too often, women and girls are limited by society and even by loved ones. We can work to change that.

Speaking in Lima, Peru, earlier this month, President Obama opened up about some of the unnecessary roadblocks women and girls face in the world.

"The leaders and the men in every country need to understand that the countries that are most successful are going to be the countries that give opportunities to girls and women, and not just boys and men," he told the audience during a question-and-answer session.

Changing the culture of limitations will take action in government, in business, in education, and yes, in parenting.

Over the years, numerousstudieshaveshown that when it comes to self-esteem, there's a major difference between boys and girls. When it comes to asking why this is the case, there are a number of theories, many of which center around culture and upbringing.

As both Obama and Williams suggest, removing the roadblocks women face in the professional world means setting girls up for success from the start. Girls need to know that they can be anything they want — astronaut, scientist, engineer, president, or even the greatest tennis player in the world.

The world needs role models and strong women who follow big dreams.

"As we know, women have to break down many barriers on the road to success," Williams writes. "One of those barriers is the way we are constantly reminded we are not men, as if it is a flaw."

For the sake of future generations, we must set aside this notion that being a woman is a bad thing and that men are the default. That's why it's important that we see people like Williams, Ruth Bader Ginsburg, Oprah Winfrey, Sheryl Sandberg, and Michelle Obama as not only some of the greatest and most successful women, but as some of the most successful people of our time as well.

The end goal, of course, must be to eliminate the unique hardships women and girls face for no reason other than their gender.

Discrimination exists in America. That's just reality. The existence of successful women isn't proof that sexism is over, just as the existence of successful people of color isn't proof that racism is over. These elements exist in society, whether they're on the basis of gender, religion, race, or a number of other factors.

One step forward, as Williams suggests, is using what others view as weakness as fuel and motivation. Until the world no longer looks at women and people of color as "lesser" because of who they are, it's important that we acknowledge just how extraordinary women like Williams are.