The coffee brain teaser is piping hot on social media and has Twitter debating brewing.
The question is simple, which cup gets coffee first?
Care to venture a guess or will you continue to percolate?
The Twitter post that went up last Thursday and has since received over 1,900 comments and been retweeted over 2,000 times asks.
Have another cup of coffee while you're at it.
And when you're ready ...
Check out the answer below, which is a bit of a trick:
Yeah, we missed it the first time, too: All of the pipes leading to the cups are blocked off at some point except for No. 5 ... which means No. 5 is the one and only one that will fill up!