A chipmunk can fit up to 34 beechnuts, each about half an inch in length, in its cheeks at one time.
Chipmunk cheeks are made of very elastic tissue, allowing the chipmunk to store a lot of food. When its cheeks reach capacity, the chipmunk will bury its stash somewhere and head back to collect more.
This ensures that it will have enough food to sustain itself during the long winter months.
In the spring, when the chipmunk comes out of hibernation, it finds the remaining stashes of nuts and seeds, if any are left, and consumes them.
As you can imagine, the chipmunk often forgets where it buried everything, and new plants sprout and grow from these hiding places.