Carl Sagan famously once said "We are all star stuff."
What could this possibly mean?
As alluded to earlier, (most) living
organisms seem to be (mostly) made
of (mostly) the same stuff. In other
words, the chemical composition of
living organisms is pretty much
similar, regardless of the kind
of organism.
We'll talk about the details of what
that composition is later on. Today,
though, we'll see where those ingredients
came from.