things like cats

and macaroni salad,

and macaroni salad is made of things

like mayo

and mustard

and celery,

which are all made of molecules.

As we'll see, these molecules

are made of the same stuff,

just mixed together in different ways.

Let's go back to our macaroni salad.

We've already unmixed things physically

as much as we can.

Now, we'll go further and unmix things chemically

by breaking some bonds.

Many larger, complex molecules

are just a bunch of smaller molecules bonded together

like building blocks.

Here, again, macaroni salad provides a nice example.

If you look at the pasta,

you'll notice it's made of a lot of this stuff,

starch,

which is this molecule,

otherwise known as amylose.

Turns out, if you break some bonds,

amylose is made up of smaller molecules

of glucose, a simple sugar.

If you take a bunch of these same glucose molecules

and rearrange them in a different way,

you get cellulose,

which is what plants are made of.

So, while this piece of pasta made of amylose

and this wooden spoon made of cellulose

look vastly different,

they're both essentially made of the same molecules,

just stuck together differently.

This type of breaking apart and recombining

is what goes on when you digest food.

The complex proteins found in the foods we eat,

like carrots and eggs,

can't be used by our bodies

because we are not carrots or chickens.

What we can use are the smaller molecules

that make up these proteins,

the amino acids.

During digestion, our bodies break these proteins up

into their amino acids

so they can be rearranged and put back together

to make human proteins.

But let's keep breaking bonds.

All molecules are made up of atoms bonded together.

If some molecules are building blocks,

atoms are the building blocks

of the building blocks.

And you'll notice that with the molecules

from macaroni salad,

the same six types of atoms keep showing up:

carbon,

hydrogen,

oxygen,

nitrogen,

phosphorus,

and sulfur,

or CHONPS.

There's a few others,

but the big six is what macaroni salad is made of.

If we went a step further,

we could use these same atoms,

recombine them,

and make other stuff

like gasoline

or sulfuric acid,

methane,

and nylon.

It's all made from the same elements

that make up macaroni salad.

So, to recap,

everything is made of atoms.

They are the stuff that things are made of.

Atoms are grouped together in different ways

to form molecules.

These molecules are constantly being combined,

broken apart,

and recombined.

They get thrown into mixtures,

separated,

remixed

over and over and over again.

The stuff that things are made of

is always in flux;

it's always changing.

Macaroni salad is only macaroni salad for a short time.

You eat it,

some of it becomes part of you,

the rest eventually goes into the ocean

and gets eaten by other animals that die,

and after millions of years, they turn into oil,

which is where gasoline comes from.

And that's why gasoline and macaroni salad

are not that different -

they're both made of the same stuff,

just one tastes better.