A neutron walked into a bar and asked "how much for a drink?" / the bartender replied "no charge."
A Chemistry Cat meme.
Chemistry Cat is a cat in glasses and a bow tie, posing with lab glassware. It's the advice animal of science puns: "I would make a chemistry joke, but I know I wouldn't get a reaction." Captions play on elements, bonds and formulas, and the best ones make you groan. It's the meme for nerdy wordplay.