Physicists may have finally found hard evidence for the existence of dark matter.
And reports from the American Association for the Advancement of Science in Boston say the announcement could come within the next fortnight - if the data holds up.
Dark matter is thought to be the invisible 'stuff' which makes up the bulk of the universe's mass. In fact it's supposed to outnumber regular matter by six to one - even though we can't see it (or at least so far).
Its existence was first proposed in the 1930s, to explain the way that galaxies expand and move in clusters. Later studies of galactic expansion, rotation and distribution added weight - literally - to the idea that dark matter may be needed to explain how the universe works.
(Nasa has a great explanation of the complex idea of dark matter - and the separate concept of dark energy - here.)
Despite the theory, it hasn't yet been possible to directly observe dark matter or even know of what it's made, but the first results from a new instrument - the Alpha Magnetic Spectrometer - are now due.
And the rumour is they could be a game-changer.
"It will not be a minor paper," said Samuel Ting at MIT, lead investigator of the experiment.
The $2 billion instrument, mounted on the outside of the International Space Station, may provide the first true glimpse at what dark matter is really like. Its job is to watch for particle collisions, and report what they are and how much energy they had.
The data could indicate the presence of dark matter if enough positrons are found at the right energy. That's because one theory of dark matter suggests it is made of WIMPS (weakly interacting massive particles) which are their own antimatter particles - and create electrons and positrons when they collide
The key is to find the "signature" of dark matter annihilations - and rumours say they might just have done it.
But don't get too excited - he added the findings were a "small step" and doesn't anticipate a true understanding of dark matter for many years. Still, this and other experiments, such as that at the Large Hadron Collider, have placed us on the precipice of a new understanding of why what we see is so small a slice of what there really is out there in the cosmos.