• Container of toothpicks
• Bag of marshmallows
• Various objects, from very light to heavy (books, blocks, containers, etc.)

1. Build a free-standing structure that is as tall and as big as possible, with 20 toothpicks and 10 marshmallows.
2. Try to have your structure support one object then try two.
3. Now add another 20 toothpicks and 10 marshmallows to your structure, and see how many objects it can support.
4. Keep adding toothpicks and marshmallows, and seeing how many objects it can support. See how big you can make it!

• Try building a new structure using the marshmallows - how many types of structures could you make? Which of them are the strongest? Which ones are not so strong?

There are numerous ways to build strong structures with things that may appear weak. The idea is to recognize that certain shapes are very strong.

The C.N. Tower in Toronto, Ontario, Canada is the tallest free-standing tower on land in the world. It is also the second tallest free-standing structure in the world. Its base is actually triangular: there are ribs that go down the length of the tower, but, if you were to look down, and draw a line around the base, it would be a triangle.

Another very strong shape is the cylinder. A single cylinder can be very strong, just not stable. If the base of the C.N. Tower were cylindrical, it would fall over with the first wind gust. However, if you make the base of a structure out of four cylinders, positioned in a square about the base of the building, then it would be extremely strong, and stable.

All structures, even marshmallow towers, are built to support a certain load. There are two general categories of loads: static loads (that do not change) and dynamic loads (that change). Within static loads, there are two main subcategories: dead loads and live loads. The dead load of a structure is the weight of the structure itself or anything else physically attached to it. Live loads are subject to change but are loads expected to occur during the regular use of a structure, such as cars or trucks passing on a bridge. Dynamic loads are sudden impacts and can be unexpected. They exert forces that are out of the ordinary, like hurricanes, earthquakes and large waves. Engineers need to think about these dynamic forces and try to construct buildings that can counteract these forces. Knowing which shapes can support load and in which way is important to design buildings with a large margin of safety, that is to say they are safe for every day use and can withstand any sudden dynamic forces.