I just had to post a picture of my fruit tower. Though visually stunning with different shades of green represented, there is a method behind my madness. The avocados and bananas aren't ripe yet so I arranged them above the apples. Apples give off ethylene gas that causes them (and any fruit around it) to ripen. This is part of the reason I don't store apples in the fridge, the ethylene gas will build up and cause them to over ripen (aka spoil). Since gas rises I arranged my avocados and bananas above the apples allowing them to ripen faster than if they were left to their own devices.