It will create the world's most valuable listed company.
That much we know about Saudi Aramco's planned share listing.
Pretty much everything else remains a mystery.
The oil giant's chairman fired the starting gun on Sunday (November 3):
(SOUNDBITE)(Arabic) SAUDI ARAMCO CHAIRMAN, YASIR AL-RUMAYYAN, SAYING:
"I'm glad to announce that Aramco has got the approval from the capital market authority for an IPO in the Saudi market".
If the sale raises more than 25 billion dollars, it will be the biggest IPO of all time.
But details were scant.
Such as how much of the company will be sold, or when the sale will happen.
Equally mysterious... just how much Aramco is worth.
Saudi Crown Prince Mohammed bin Salman wants a two trillion dollar valuation.
That's about twice the worth of Apple or Microsoft - currently the world's most valuable listed firms.
But analyst estimates vary - by a mere trillion dollars or so.
Some put it the price at just the one trillion.
Goldman Sachs, sources say, might go to 2.3 trillion.
Aramco is certainly hard to value.
No one doubts its massive oil reserves, or its immense profitability.
But it's closely entwined with the Saudi state, and famously secretive.
It's also still recovering from attacks on its facilities, which initially halved output.
Though Aramco says that won't have a material impact on operations.
Now Reuters sources the share price will be announced in late November.
That should clear up one mystery, at least.