Jennifer Lopez just brought back the most detested '90s trend (and somehow made it look good).

Image via Getty.

Jennifer Lopez celebrated her birthday over the weekend, and like most of us pulled out all the stops with a killer outfit and smile to match.

But while much attention has been paid to her dress (for the record, we think she looks amazing), there’s something else we can’t stop looking at – her makeup. More specifically? Her lips.

THOSE LIPS.  (Photo by Jerritt Clark/Getty Images)

Yes, Jennifer Lopez has managed to bring back arguably the most detested '90s beauty trend, and made it look incredible. Visible lip liner, take a bow.

Flash back over 10 years ago and dark brown lip liner was an essential tool in anyone's makeup bag. In fact, the starker the contrast between your lip liner and lipstick colour the better. (Post continues after gallery.)

Unsurprisingly, Lopez was an such a champion of the bold lip look through the nineties and early 2000s, that the "J-Lo Lip" was the most requested makeup look, according to makeup artist Ashley Ciucci.

RELATED: “Short hair, don’t care.” Jennifer Lopez goes into Phase Two of her short hair plan

While it seems to go against every lipstick tip we use today, the 46 year old still manages to make it look awesome. The secret? Keeping the tones as similar to your natural colouring as possible.

Jennifer Lopez in 1999. Image via Getty.

And although matte seems to be having its day, the trick with this look is all about shine. Using lip gloss rather than lipstick will soften the liner and also give it a shine for a subtle plumping effecting.

In terms of colour, again stick to a nude or peach colour. Not sure where to start? We reviewed some of our favourites nudes for all skin tones. (Post continues in and after gallery.)

Although the singer's look for her 46th birthday is straight out of your favourite '90s rom com, there have been a few signs of it creeping its way back in - in the form of ombre lips.

A more modern and creative twist on the classic dark lipliner and lighter lipstick combo, ombre lips are designed to make lips look fuller.

RELATED: “How do I find the right lipstick for my ‘skin tone’?”

The technique requires two lipstick colours in similar shades, but different tones - i.e one darker colour and one lighter.

Simply apply the darker colour all over your lips, then dab the lighter colour in the centre of both the bottom and upper lip.

Ombre lips, the modern equivalent. Image via Youtube (@Topshop)

The look works really well in bright colours like pink and red, but would also work in more natural nude colours if you're after a subtle look.

Would you try ombre lips? DO you think the dark lip liner should make a comeback for good?