The Last Molecule

 

Source - https://xkcd.com/2552/

See it's funny because there's no way that chemistry - or any science, really - will ever be 'complete'.

I'll quote here from the explainxkcd.com entry because it's really well written (as is usually the case)...

"[T]this may be a reference to a quote from around 1900, often attributed to Lord Kelvin or Albert Michelson: "There is nothing new to be discovered in physics now. All that remains is more and more precise measurement."

...

"In real life the number of ways to arrange atoms into molecules grows combinatorically with the number of atoms in a molecule. Since molecules can be extremely large (up until the point where gravity takes over and initiates nuclear fusion), the number of possible combinations is much much larger than the number of particles in the observable universe, making the full cataloging of all molecules impossible. Thus, a "final molecule" cannot be reached. In addition, chemistry is the study of the interaction and changing states of atoms and molecules, not simply the cataloging of all specimens of molecule. Even if we did have a list of every molecule, there are a far greater number of ways to continue studying them, so the field would still be nowhere near completed."

...

"As readers are aware of this, part of the humor comes from the very high percentages given to the different fields. [...] Another part of the humor is the precision."

Jokes for nerds, folks, jokes for nerds!