What is the HEADstrong Foundation, and why do you keep seeing it on Instagram?
Have you been tagged yet?
If you have been on Instagram at any point in the past week, there is no way you have missed the stories of people sharing images of them playing sports, alongside the caption @HEADstrongfnd.
It is also expected that you tag three people after you upload your picture, and they are then expected to do the same.
There has been a bit of confusion surrounding the whole thing, with many wondering why people were uploading these pictures.
The original idea behind the viral challenge was so that both male and female athletes would post a picture of themselves while playing their sport of choice, and would tag the charity's official account in an attempt to raise awareness for HEADstrong Foundation, an American-based charity which offers support to families affected by cancer.
It was originally set up following the news that an American lacrosse player named Nick Colleluori was diagnosed with extremely rare form of cancer. She joined forces with the charity, and it has gone worldwide since.
A number of professional footballers have got in on the trend, including Ireland's own Robbie Keane, who tagged Nigel DeJong, Steven Gerrard and Shay Given.
The HEADstrong Foundation themselves seem shocked by just how viral the challenge went. They took to Instagram to inform people that they had seen that people in Wales were taking part, and said that "the campaign is on fire".
More information on The HEADstrong Foundation can be found on their official website.