My grandchildren were learning the metric system and needed some physical representations.

The 1cc box shows 1 cubic centimeter or 1000 cubic millimeters.

When the 1cc box is filled with water it is 1 gram of water.  It is also 1 millilitre, or 1/1000 of a litre.

The 1 litre box is 10cm x 10cm x 10cm or 100mm x 100mm x 100mm or 1 decimeter x 1 decimeter x 1 decimeter inside.

The litre box is 1000 cubic centimeters. (10cc*10cc*10cc) or 1 million cubic millimeters.

The litre box when filled with water is 1 kilogram of water. 

These examples help show how the metric system of measurement, weight and volume are all linked together.  Water is the base element for converting volume to weight.  

Adults that haven’t grown up with the metric system quickly understand the relationship.

For little kids having them fill the 1cc and pour it into the litre 1000 times can keep them busy for a while.