There's a good reason to look closely at tennis players' nails this Aussie Open.

With the Australian Open over halfway through, tennis fever has officially hit.

Balls are being hit from morning until late and most of us are going through our annual “wow, tennis players’ strength/skill/athleticism is seriously impressive” realisation as we (briefly) contemplate taking up the sport ourselves.

But allow your eyes to go past the flying balls, adorable ball boys and girls and speeding rackets for just a second and you might notice something else taking over the court, thanks to the female players.

Yes, I’m talking about nails.

Daria Gavrilova favours a darker polish. Image: Getty

From colourful designs to simple white falsies, players from all over the world have a manicure to match (ha!) their incredible skills.

When you're restricted to wear a uniform (of sorts), players - and athletes in general - often look to makeup, hairstyles, jewellery and nails to express their personality.

And Serena Williams has an extra advantage over most.

The 35-year-old dominates women's tennis — she's won a casual 22 grand slams and is generally regarded as one of the greatest tennis players ever, just FYI — but she's a serious overachiever off-court, too.

Williams has designed lines for Puma and Nike, is the face of Berlei and created her own fashion line Aneres. Plus, she's launched a collection of handbags and jewellery.

But it's her nail polish collaborations with brands like OPI and HairTech that really set her apart. Because in preparation for these endorsements, Williams decided to get certified as a nail technician (as you do).

Image: Getty

"No one likes getting their nails done more than I do.  As a matter of fact, I go every four days to get a manicure and every seven days for a pedicure... I thought ‘Serena, this is a no-brainer’," she wrote in a blog post for Global Grind.

This was in 2010, around the time Williams was dealing with what looked like a potentially career-ending leg injury which had already sidelined her from five tournaments.

Williams told Time that as she had "a little bit of time on [her] hands," she enrolled in a course that required her to complete 240 hours of practise in order to get certified, which began straight after she returned home from the Australian Open in January that year.

Proving she's a woman who never does anything by halves, Williams applied some of what she'd learned in tennis training to the course, spending the night before preparing all her tools, books and gear. (Post continues after gallery.)

As you'd expect, her competitive nature remained strong.

"Before bed I stayed up studying for a few hours so I could be ahead of the class. Not only do I plan on being the top student to graduate from my nail school, but I also intend on being the most fashionable!" she wrote at the time.

While her love for fashion is well-known (naturally, she also has a fashion degree), even Williams was forced to comply with the regulation blue scrub uniform, after her enquiry as to whether she could wear pink instead was rejected.

On her first day Williams had to do a pedicure, which she aced.

"Luckily, thanks to my weekly pedicures I took my time and it came out great. I know it wasn’t just me thinking I did good because all of the other girls kept asking if I had done this before," she wrote.

Although the hours are usually completed in six weeks, at the time Williams planned to finish her course within a year.

While it's not clear how long it actually took, in a June 2012 interview with Time, Williams said she was certified.

And if her fingertips on court since are anything to go by, her nail game is just as strong as her tennis one — and that's seriously saying something.

Have you ever noticed Williams' nails before?