system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are fleas the size of a speck of ground pepper but they can jump so high?
gpt
Part of the answer is the relationship between size and mass.  If an animal is half the size, it's one-eighth the weight - so the smaller an animal is, the stronger it is in relationship to their weight.  This allows very small animals to perform relatively amazing feats of strength.

Additionally, fleas have a special adaptation for jumping - rather than flexing their muscles to leap into the air, they repeatedly flex their leg muscles to put tension on a "spring" made of elastic protein.  Then they release that tension all at once to jump.