25 December 2013
Last updated at 13:51 GMT
Selfies - pictures people take of themselves - have been one of the big talking points of 2013.
"Selfie" was even named "word of the year" by the Oxford English Dictionary.
But what does the phenomenon say about the people who take them, and about society in general? #BBCtrending speaks to two experts - Lisa Orban and Andrew Przybylski - about the psychology of the selfie.
Produced by Dougal Shaw
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