Children love balloons. Helium balloons are especially fascinating because of their unique "floating" qualities. If you have one left over from a party, or have the chance to purchase one during a shopping trip, try something new with your child.
First, make sure to give your child plenty of time to play with the helium balloon independently. Then help your child tie a tiny toy to the balloon and let it go (make sure you are inside!).
What happens? Can the balloon lift the toy into the air? How far does the balloon go? Does it stay up?
Try again with a different toy, maybe a different size or weight. If you have more than one balloon, try lifting small toys on each at the same time.