So for this you need:
1 huge ass jar
Crap load of golf balls
bucket full of pebbles
bag of sand
The experiment is to see which order to put things in the jar so that the most of each kind of item can fit.
If you fill the jar up with sand first, you'll see no room for the golf balls or pebbles.
BUT if you fill it up with golf balls first, pebbles 2nd and sand last, You put in a good combination of items into the jar.
The point is, if you fill the jar with the smallest objects first, you have no room for bigger things inside of it.
See how it ties to life?