How would you explain cellular respiration to an eight year old?

I am working on a biology project and have to explain the processes of photosynthesis and cellular respiration to kids from ages 8-12! Impossible right! I would really like some help. Anything would be great.
Update: I've gotten some nice answers so far. I have managed to explain most of the process execpt for the electron transport chain... how should I explain NADH and FADH (electron carriers)? Please help!
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