Just this morning, we were discussing the new images of the Samsung Galaxy S8 - with a new key that didn't seem to have a place.
The power and volume rocker keys made sense - after all, it's hard to remember a phone that didn't have those things - but the best we could surmise is that the extra protrusion was for a 'convenience key' in the same manner as the BlackBerry / Alcatel range.
But just a few hours later Samsung has furnished us with the information to explain: it's for activating Bixby, its Siri-cum-Alexa-cum-Google Assistant rival.
In the same launch, Samsung took the odd choice of confirming that the launch in a few days' time will be for the Galaxy S8 - of course, it's hardly a surprise but most brands (who aren't LG) will keep the name of the phone locked down until the event, preserving the worst-kept secrets.
But which is it?
The bigger question is 'which key is it?' that controls the Bixby assistant - our money is the one below the volume keys, as it's the less-used area of the phone for the right-hand dominated world we live in.
However, we can see this irritating the bejesus out of lefties, as that's where the finger will naturally rest and could see accidental activation - but we assume Samsung will have thought this through.
It's interesting to see the Galaxy S8 packing such a feature though - given it clearly sees Bixby as a function for the future, and it seems many apps won't be 'Bixby-enabled' at launch, it seems an odd investment to have an extra piece of hardware eating into profits.
And what will happen with Google Assistant? Presumably long-pressing the home button will activate this function, and if Samsung couldn't remove that then it explains why there's a dedicated hardware key to solve the problem.