Donald Trump says he's sacking Federal Reserve governor Lisa Cook.
She says she's not going anywhere – and is threatening legal action.
No one quite knows how this will unfold, or whether it could end up in the US Supreme Court.
What's clear is that it's highly unusual – and it's raising serious questions about the independence of America's central bank.
For months, the US president has been piling pressure on the Federal Reserve, demanding interest rate cuts to give the US economy a boost and make it cheaper for the government to borrow.
