Pope Francis has done it and Michelle Obama has done it (with the First Dog). They're what's now known as selfie artists.
If you do not know what a "selfie" is, you are now officially out of the loop, according to Oxford Dictionaries, the publisher of the venerable record of the language of Shakespeare and George Orwell. "Selfie", it has decided, is the word of 2013, joining an annual list that has been surprisingly accurate at summing up the zeitgeist. "Chav" was the word of 2004, "credit crunch" was 2008's, while last year it was "omnishambles".
A selfie is a self-portrait taken on a camera – invariably a smartphone – before the taker uploads it to a social network, such as Facebook, Instagram or Twitter for their friends or "followers" to see and "like". As Fiona McPherson, senior editor at the Oxford English Dictionary, says: "It's not just taking a picture of yourself; the publishing of it makes it a 'selfie'. So, 'self portrait' doesn't quite cut it as a term."
It is an act as modern as it is narcissistic, perfectly capturing the self-regard of our age. But it is also, some think, a worrying trend that could leave young girls, in particular, with low self-esteem.
The history of selfies is linked to the rise of technology and the cult of the celebrity. The first recorded use of the word was in 2002 when an unnamed Australian student posted a picture of his split lip after a drunken party. "Sorry about the focus, it was a selfie," he wrote on an online forum.
Of course, being the first person to write down a word does not mean they invented the term. Jane Austen takes credit for being the first person to record "family portrait", "door bell", and "flower seed". All of these existed long before the Regency era. They just were not written down.
The gap between first utterance and first recording, however, is becoming ever shorter, thanks in part to social networks. The youth of today write far more words per week than their grandparents ever did.
They may not be as eloquent, but the gush of texts, tweets, and blog postings greatly help dictionary compilers, who can scan the digital landscape for new words.
"Selfie" appeared 97 times per billion words in 2012; it has appeared 5,416 times per billion this year.
This explosion in popularity is partly down to the smartphone. Two years ago, 27pc of adults had smartphones, capable of uploading pictures to the internet. That figure has doubled and is climbing fast.
But it was the development of phones with rear and front-facing cameras that made selfies possible. Before, you had to perform a yoga-stretch with your arm to take a photograph that actually had you in the frame. Kat Hannaford, editor of the website Gizmodo UK, says: "The manufacturers starting pushing it as an idea once they had front-facing cameras." At the same time, the technology companies were fully aware of the rise of celebrity culture, with Polaroid hiring Lady Gaga (one of the pop world's biggest selfie takers) as its "creative director".
The nature of celebrity has changed rapidly. Pop singers and actors are as influential as ever, but the emergence of stars created by reality television have become equally important. And it is no coincidence that the person responsible for more selfies than any other celebrity on Instagram, the photo sharing network, is Kylie Jenner, who at only 16 has 6.45 million followers.
She found fame in America by appearing in a reality programme about her family, called Keeping Up With the Kardashians, and the Kardashians, indeed, have been instrumental in pushing the selfie and even the "belfie", "bum selfie", which involves not just pouting into the lens but thrusting out your behind.
Kylie and her sisters Kim, Kendall, Kourtney and Khloe are typical of the high-profile selfie brigade: female, young, often wearing a bikini and whose main occupation is self-promotion and the seeking of affirmation from their followers.
In the old days, self-promotion needed the connivance of the tabloid press. Now, celebrities can push their latest line of jewellery, perfume, haircut or themselves, directly, free of charge via social networks.
But it is not just trashy TV stars who do it. Hillary Clinton can hardly stop snapping herself, while the picture of Hollywood actors Bradley Cooper and Gerard Butler taking a joint selfie in the royal box at Wimbledon this summer was proof they were having a ball.
We should not be surprised, therefore, that the thousands of celebrity selfies have bred millions of ordinary selfies, not least from teenage girls, desperate to win the approval of their peers. Emily Lovegrove, a psychologist who specialises in bullying, says: "Kids are hardwired to copy adults. And when they see – in their eyes – successful adults, they want to ape their behaviour."
Girls in particular, she says, seem prone to copy celebrities when it comes to selfies "because they understand that looks are important, however much adults tell them they are not. It is now accepted that fame rests not just on talent, but the ability to self-promote." A few "likes" on their picture can make their week. Equally, selfies can be used to poke fun, or worse.
Of course, many of the celebrity shots are artfully stage-managed or even photoshopped. Miranda Kerr, the lithe underwear model, was accused of touching up an Instagram picture to make herself appear even thinner. She soon removed the picture, saying she "had no idea it was photoshopped".
As Lovegrove says: "An awful lot of girls do not realise this [manipulation] and it makes it even more likely they will strive to attain impossible perfection." Yet though this may damage their self-esteem, selfies become more problematic if the sender strays into sexting – sending nude pictures of themselves to a boyfriend or girlfriend.
Still, while parents may wring their hands, the urge to self-promote has been with us since Georgian families hired Gainsborough to paint their portraits. It is just much cheaper now.
As Dr Lisa Orban, a psychologist, says: "Experimenting with self identity is a key part of adolescent development.
"And today's technology allows a strong element of control. It is easy to dismiss selfies as narcissistic, but this safe and controlled self-exploration is particularly important for younger users."
Perhaps we should be worried not about teenage girls, but about grown men – including world leaders – who love nothing more than a selfie.