What are little boys made of?
Snips and snails
And puppy-dogs’ tails
That’s what little boys are made of

What are little girls made of?
Sugar and spice
And all things nice
That’s what little girls are made of

There are several ways we could measure what we are made of. We could classify ourselves as amounts of fat, bones, and muscle. Or maybe we could express ourselves by percentage of water (about 50-60% if you really want to know).

 At the Lowest Level

At the most basic level, people are made of the same stuff that everything else is made of-namely, atoms. The atoms make up molecules, and the molecules make up chemicals. We can also classify ourselves by the chemicals in us.


If we go by chemical composition, we are mostly carbon…


 How Efficient is the Human Body?

We can compare the efficiency- defined as work done divided by energy consumed-of the human body with the efficency of other machines.

  1. A human can get up to about 20% efficiency by cycling on a stationary bike.
  2. The top efficiency of a petrol engine is about 38%, but most are around 20%.

So we are as good as most engines! – pretty neat huh!