Q: Why don’t scientists trust the atoms they work with?
A: Because they make up everything!

Explanation: Everything is made of atoms.  Yes, those atoms, the ones that are found on the periodic table of the elements.  It is still hard for me to believe that those little atoms make up the air we breathe, the trees that grow, the metal in my fork and knife.  In this case, to make up something means that it is a part that makes up the whole of something.

To make up also means to invent or to create.  When authors write a new story they make up that story.  To make something up can also mean to lie.  If a student arrives late to class he or she might make up a story about the late arrival; a student might make up a story about the missing homework (“My dog ate it!!”).

This joke is funny because it plays with the words make up, meaning the parts of something or inventing a story.  And you can’t trust someone who is always making things up!

Someone you can trust is Venus Flytrap from WKRP in Cincinnati.  Here he is making up a story to explain how atoms make up everything-