Genes code for all the protein components of the body. Basically, genes are the information storage of heredity. The human being has a total of 100,000 genes, give or take, and that sum total of all the genetic information is called the “genome.” If we can completely understand the structure of the human genome, then we have a complete component list of all of the proteins that the body makes. In a sense, that goal, the Human Genome Project, is very much akin to the revolution in chemistry that happened in the period of about 1869 to 1889, when all of matter was described in terms of a finite list, a finite chart that captured its properties. That changed the face of chemistry, because it meant that matter was predictable, through only a finite number of elements. Biology now is getting its own periodic table. In the 21st Century, we will know that the human body is composed of some set of 100,000 proteins, and all biological programs will start from that list. If you want to understand any particular thing, you’ve got to understand it in terms of those components. There aren’t any more components to go look for, at least at the level of proteins. So the effect on biology in the next century will be much like the effect on chemistry in this century. For chemists, the predictability of matter gave rise to industries, the chemical industry. The mysteries of the periodic table, and why there were rows and columns of elements, gave rise to some of the deepest theories of this century, quantum mechanics. I think so, too, understanding the component list of the human body, the human genome, will give rise to both very practical consequences and very theoretical consequences. The students looking back, 20 years from now, will not be able to imagine what it was like to practice biology without these tools. Indeed, they’ll assume they were always there. They will look back to this earlier period with a romantic notion, like 19th Century African explorers going off into the jungle with their machetes, searching for a gene and sometimes coming back triumphant with a gene in hand, and sometimes never being heard from again. But that romantic picture of exploring the deepest, darkest continent of biology will be replaced by a Landsat image with accuracy down to the single DNA letter. It will be a very different world, and it will be hard to imagine what anything was like before it.