For 4 billion years, DNA has twisted, turned and spread itself around the Earth in seemingly infinite forms.

Making up the blueprint of all living—and maybe not so living—organisms on the planet, DNA is the record for all life on planet Earth. Despite such a storied career, it was less than 200 years ago when we finally started to understand what DNA is, what it does and why it matters so much for health.

In the mid-19th century, a Swiss chemist looked for the basic components of life. What he called "nuclein" is what we now call DNA. From there, scientists steadily discovered more about the <link explore whats-here exhibits genetics-and-the-baby-chick-hatchery>blueprint of life.

Briefly, biochemists found the genetic building blocks: the As, Ts, Gs and Cs. Geneticists established the link between DNA and hereditary traits. Biologists showed that DNA packed into chromosomes. But how DNA became the diverse blue feathers, sleek fins and spindly stalks of life remained a mystery ... until 1953. When James Watson, Francis Crick, Rosalind Franklin and Maurice Wilkins discovered the structure of DNA, we could understand how DNA could be translated into the feathers, fins and stalks of life as instructions.

Still, we didn't know what the instructions said. Then in 1990, the Human Genome Project began.

In this month's Science News' Century of Science theme, The Human Blueprint, senior science writer, Tina Hesman Saey interviews Dr. Eric Green, one scientist of a group working together to unravel one of DNA's greatest mysteries: the 3 billion genetic building blocks—the As, Ts, Gs and Cs—that make up the human genome.

"We had some ideas on how to start, and we really had no idea how we were going to pull it off," said Dr. Green, a common thought among revolutionary innovators, like those who designed the <link explore whats-here exhibits pioneer-zephyr>Pioneer Zephyr.

By 2003 the Human Genome Project released 90% of the human genome sequence (and with advances in technology and computing, scientists finished the last 10%), an accomplishment celebrated every April on National DNA Day.

But what can that tell us? Why is it important?

In those three billion building blocks is a shocking amount of diversity and variation. Ranging from variations in a single letter, to strings of letters, to extra or missing segments - every single person's genome is unique. As scientists are gaining more traction with understanding the breadth and meaning of genomic differences, one thing is becoming clear:

"All forms of genomic diversity are not only biologically relevant, they're all proving to be medically relevant," said Dr. Green.

Even the smallest changes in DNA, placing an A where there should be a G, for instance, can drastically impact a person's health—and dictate what treatment will work. Fine-grained genomic approaches like these are improving medicine, but personal genomics is just that: personal. And our society has a tendency to group things and people together in ways that muddy the water rather than clarify it.

"The truth is, of course, there are certain [diseases] that tend to cluster in certain populations of common ancestry," said Dr. Green, "and many times these are represented by racial groups."

Yet race is a social construct, not a biological one. Applying a social construct to a biological construct is like measuring something's weight with a yardstick: both are measurements, but you'll never get the kind of true measurement you need. To get the most of genomic medicine, we as scientists and as a society need to make sure we're using a scale, not a yard stick.

"The way we could do this better," says Dr. Green, "is to track much more accurately to specific genomic features, as opposed to racial characteristics."

Such specificity requires progress in three areas: cheaper sequencing, sequencing in communities from all around the world and (most importantly) health and medical care benefits to everyone.

"I absolutely envision a time where people will get their complete genome sequenced end to end as part of their medical care," said Dr. Green.

For that information to benefit everyone, we have to continue doubling down on programs like the Human Hereditary and Health in Africa program that empower scientists to blow open the doors on cheaper sequencing all around the world by engaging their own communities.

Said Dr. Green, "It's been a success by every metric."