and the idea that all living things are made up of cells

that we as human beings, as living organisms, we are made up of many, many, many cells

the estimates of the cells, of the human body, are around the order of 37 trillion cells!

But, if we were to rewind, even 400 years ago to the 1600's

this wasn't so obvious.

and that is because people really didn't have the tools

to make direct observations of cells. They didn't know that these cells were around.

They didn't know that things, even like unicellular organisms, even existed!

But, all of that began to change, with Robert Hooke.

Robert Hooke, was able to leverage a primitive microscope

and this is a picture of his microscope

and when you see this, you appreciate how

at least relative, to what we have today, how primitive it was.

He had lenses here, that would provide some magnification,

but he had to use -- this right over here -- this is a flame, and he is able to channel that light

so that it gets reflected over whatever he is observing.

And in, 1665, he publishes the "Micrographia".

I am probably not pronouncing it right.

So, this is 1665, Robert Hooke publishes this

and in this, he describes and he draws a lot

of his observations, using his microscope.

He has some fascinating drawings, he was actually quite a good artist,

where he was able to draw pictures

of his observations, of things like lice, and fleas.

But, it's not just lice and fleas that he is able to observe.

He actually takes a look at some corks or what he just sees as "cork"

and when he makes that observation, he says, "Hey look, you know there are these little squares over here, and this kind of seems to be somehow kind of a basic unit of this cork. "

And he says, " Well, this kinda reminds me of these little rooms that monks live in and spend their time in, which we call cells".

So he calls these cells.

And, that is where the word comes from.

He calls them cells, in "Micrographia".

That is a cell.

Now unfortunately for us, he was a great artist

and he was really good at drawing things

and he drew a lot in his "Micrographia", but we don't have any pictures of Robert Hooke anymore.

And it's a fascinating story. Most theories are that

actually, it was Isaac Newton, who burned the only original painting, that we have of Robert Hooke.

And, that is another intriguing story, that we can talk about, at a future date.

But, what Robert Hooke — he coined these things "cells" — but he was looking at dead tissue, and actually he was