On March 8 each year, International Women's Day celebrates the achievements of women past, present and future - and also serves as a reminder of the inequities that still need to be addressed.
This year's theme is 'Inspiring Change', something the WTA has strived to do ever since its formation at London's Gloucester Hotel in 1973.
Originally set up in protest to the staggering disparity in prize money between men and women, the WTA has gone on to become the standard bearer for professional women's sport. Today, it now boasts a cast of over 2,500 players representing 92 countries, competing for $118 million in prize money each year.
In some countries, including Russia, International Women's Day is a national holiday, and despite being at work in Indian Wells on Saturday, two of the game's brightest stars found time to pay their dues.
"We get to be here playing tennis, but not a lot of women get these opportunities, whether it's playing sport or getting the education they want. I'm very grateful to tennis and the WTA and what Billie Jean King did for our sport.
"I want for every woman in the world to have the ability to do the things that they want to do and have equal opportunities to do it.
"In Russia it's a very big holiday. We don't really think only about the achievement of women, it's more just a day where all guys bring lots of flowers and give us complements and stuff like that! It's a huge thing for us."
"We've created an incredible international fan base for our sport. I think what we do and the sport itself is so entertaining to watch. Stars have developed from different areas all around the world and it's great to see how we have so many international players in the Top 10 right now.
"To every event we go and each city we travel to, we see that excitement build up. We see it before the tournament, during the tournament, and it's very inviting to see as a player."
For more information on this year's celebrations, visit www.internationalwomensday.com.