# 4: Focus on the microworld

Notice how micrometres have a lot of names? You can call them microns (this will sound like you know what you are talking about, in case you have a crush on a biologist), or you can call them micrometres (accent on the o), or “um”, or use the Greek letter, µm.

Microns got so many names because in a lot of ways, they have received the most attention from biologists. From the invention of the optical microscope in the 1600s all the way until the mid-1900s, biologists have been able to see into the micro-world, but not farther. So, naturally they came up with a lot of terms for micrometres.

The microworld has been very important in biology, and youll spend much of your first year in biology getting familiar with what happens there. And we actually can do a little bit of hands-on measurement of the microworld.

What we’ll do is measure a stack of thin things in order to figure out how many microns each individual thin thing is. Got it? Good.

For example, take your ruler and measure 1 millimetre worth of pages in your textbook.

How does this relate to microns? Recall that 1 mm is 1000 µm. So, for example, if there were 2 pages in a millimetre, you would divide 1000 mm by 2 to figure out that each page was 500 microns thick.

Now type your real data below:

I got 14 pages to the millimetre in my textbook, which made my pages 71 µm each (approximately). Just for fun I tried it with:

a stack of business cards (200 µm each),

the Brisbane White Pages (61 µm each), and

and toilet paper (100 µm each).

So in general I think we can conclude that most paper is around 100 um thick. Squarely in the microworld.