For almost as long as we've had mobile phones, we've had concerns over whether they were "frying our brains" - despite a lack of conclusive evidence.
Then, at the end of last year, a Swedish study was released claiming that people who regularly used a mobile phone for more than 20 years were two to three times more likely to develop a brain tumour. Even the World Health Organisation has now classified cell phone radiation as posing as carcinogenic risk to humans.
But it doesn't seem to make sense - scientists know that mobile phone radiation is non-ionising, which means it's not strong enough to rip electrons off atoms or molecules and destroy DNA. There's no logical reason that mobile phones should cause tumours.
So what are we supposed to believe?
In the powerful episode above, Derek from Veritasium breaks down the conflicting evidence surrounding mobile phones and brain tumours, and also explains why the methodology we're using to test the link is fundamentally flawed.
In fact, Derek argues, the answer to the question is far simpler than you might imagine, and the large-scale, conclusive evidence is staring us in the face. Watch the video above to find out the truth.