A backpack is a recurring item used for storage in the Mia Collection series.
Mia virtually always wears a backpack with her wherever she goes. In the Learning Adventures games in the Mia Collection, Mia's backpack is used to store items that the player finds while playing that may be used later, such as Sparklies. Mia's skateboard is almost always contained in her backpack as well.
The backpack is capable of storing items of many sizes, even if those items are much larger than the backpack itself.