Singer Selena Gomez performs during her Stars Dance Tour at Staples Center in Los Angeles

"#14yrsStrong"

That is how Demi Lovato describes her friendship with Selena Gomez, in reply to her best friend's photo of the two of them over the latter's Instagram account.

The photo posted on the "Love You Like A Love Song" singer's Instagram account (@selenagomez) was taken backstage of The X Factor set, where she appears as a guest performer while her best friend Demi is a judge.

The caption reads, "It's just the evidence of forever. No Matter what @ddlovato," which the "Heart Attack" singer responds with "Love you SO much.. #14yrsStrong".

As of writing time, the photo got 608,000 likes and 42,800 comments.

Gomez's performance in the reality competition, however, was rescheduled due to technical problems in the contestants' voting system. This means fans can expect more selfies from the duo.

Selena and Demi met on the set of Barney and Friends when they were seven years old, and bonded more during their tenure in separate shows for Disney. They had a brief fall out which ended in 2009, and have remained strong as friends since then; bonding over little moments they are together such as their guesting with Jimmy Kimmel Live last October and now in The X Factor.

Selena even admired Demi for her courage in overcoming personal issues which includes her stint in rehab.

"I'm very proud of Demi and her being able to accept the challenges she went through, but also for staying a good role model to people who do struggle with the things that she's gone through," Selena told i-D magazine.

"If you surround yourself with good positive people you can only do good things for them and they can only do good things for you," she tells further.

Aside from her judging gig in The X Factor, Demi is also busy with her acting gig on Glee and preparing for her Neon Lights tour with Fifth Harmony and Little Mix. Selena, on the other hand, is currently on the road for her Stars Dance tour.