I Just Must Be Dumb (1 cent)

From today's New York Times (with my annotation):

For thee billtion years, life on earth consisted of singled-celled organisms like bacteria or algae. Only 600 million years ago did evolution hit on a system for making multicellular organisms like animals and plants. (so far, so good)

the key to the system is to give the cells (whatever that is) that make up an organism a variety fo different identities so that they can perform many different roles.

So even though all the cells (whatever they are) carry the same genome (whatever that is), each type of cell must be granted access to only a few of the genes (whatever they are) in the genome (whatever that is), with all the others permanently denied to it.

People for instanc,e have at least 260 differnet types of cells, each specialized for a different tissue or organ, but presumably each type of can activate only some of the 22,500 genes in the human genome.

the nature of the system that assigns the cells their various identities is a central mystery..........

They have discovered a striking new feature of the chromatin (huh?), the specialized protein (what is that?) molecule (huh?) that protect and control the giant molecules (who are they?) of DNA (what is that?) that lie at the center of every chromosome (whatever they are).

I am just dumb. But, for years, I have failed to understand any of this.