# Focus on the microworld

Notice how micrometers 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 micrometers (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 gotten 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 micrometers.

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.

So getting out your micron ruler… never mind.

Instead, 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 of 1 millimeter worth of pages in your textbook.

No, really, do yourself a favor and get out a ruler.

Or at least take a guess.

How does this relate to microns? Recall that 1 mm is 1000 um. So, for example, if there were 2 pages in a millimeter, 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 millimeter in my textbook (“Environment: The Science Behind the Story, edition 2), which made my pages 71 um each (approximately).

Just for fun I tried it with:

a stack of index cards (200 um each)

the Washington DC Yellow Pages (67 um each)

and 7th generation Unbleached toilet paper (100 um each)

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