100 trillion good bacteria living on the human body - Paul Rockett

You can count numbers all around you, from the eight legs on a spider to
the one nose on your face. But can you count the stars in the sky or
the fish in the Amazon? Find out all about the THE HUMAN BODY in THE BIG COUNTDOWN, including the millions of bacteria that live in and on us and help our body function healthily, our digestive system, our bones and muscles, our blood and heart, our lungs and breathing, the size of our brain and the number of hairs on our head. It also covers the human life cycle and the development of a foetus in the womb.

The Big Countdown looks at popular
topics and investigates the great many numbers that make them
fascinating. From the mind-bogglingly large to smallest and most
precious, this series helps us understand that it's not just our days
that are numbered.