For the first time in history, crude oil in the US has collapsed into negative territory.
It means traders - have effectively - been paying anyone to take it off their hands.
The problem is there's too much supply, and not enough storage capacity.
Alan Breen from Cantor Fitzgerald explains what happened.
"It was quite extraordinary and unprecedented in fact.
"WTI crude for May delivery came under massive pressure yesterday and fell below $1 for the first time in history.
"The sell off was driven by the expiry of May contracts today, but also the more active June contracts also came under pressure."
