After he discovered the secret of life, Francis Crick had to figure out what else to do with himself. We can all relate to this dilemma. Your resume says, "Discovered secret of life," but that achievement is way in the past, in your youth. What have you done lately?

Crick decided to spend his last few decades trying to explain the phenomenon of human consciousness. He wanted to know how something as vivid and strange as self-awareness could emerge from a piece of meat, a tangle of neurons crammed into a skull. Crick failed. When he died Wednesday at the age of 88, he could be credited with only one of the greatest scientific breakthroughs in human history, not two.

There have been more important scientists than Crick. But he had the courage, arrogance and gall to ask really big questions, and on a February day in a laboratory in England in 1953, he and his partner James Watson found one stunning answer. The two men, after a year and a half of noodling around with models, quaffing brews in their local pub, wandering the streets of Cambridge and peeking at the work of their scientific rivals, deciphered the structure of the molecule that functions as the blueprint for life on Earth.

This molecule, DNA, had been waiting for billions of years for someone to come along and appreciate it. It was a thing of beauty, twisted in a double helix, the very structure screaming the answer to the mystery of how one living thing can pass along information to a descendant. No instrument could see its structure directly; its discovery required two people wielding the powerful instrument of human imagination. They didn't directly detect the structure of DNA, they figured it out.

History is full of these things that patiently wait for someone to understand them. White light is a compressed rainbow: Newton and his prisms finally saw the truth. There are stars in the Milky Way, mountains on the moon and worlds orbiting Jupiter, all unknown to humankind until Galileo looked at the night sky with a new contraption called a telescope. Mysterious nebulae revealed their true nature to Edwin Hubble and Milton Humason on a California mountaintop in the 1920s: They were separate galaxies, immense pools of billions of stars.

Of all the breakthroughs in biology, the greatest was that of Charles Darwin and Alfred Russel Wallace, who in the mid-19th century grasped that all life is related and evolves through natural selection. It's still a stunning thought. Lots of folks don't even believe it. Humans are not just related to monkeys, they're related to pond scum.

The Watson-Crick discovery, aided by the X-ray crystallography of the largely unheralded Rosalind Franklin, ranks as the most important moment in biology in the past century. The breakthrough eventually led to the manipulation of the genetic code and the rise of biotechnology, which will merely change life as we know it. In a thousand years, when everyone is genetically engineered, rendered immortal, beautiful, brilliant, with perfect skin and hair, living in a world in which a pimple is considered a freak biological disaster, people will still talk of Watson and Crick.

Science and religion may never agree on whether the twisted double helix is something that evolved from an earlier form of genetic material or is the result of a divine designer. But there's no doubt that it's an elegant, inspiring molecule. Artists love it. It may become the iconic image of the 21st century. If you make a big-budget movie in which someone is genetically altered in an experiment gone awry, you have to show double helixes spinning and distorting and turning green and so on.

Life is inextricably connected to structure. Our human fascination with architecture, landscaping, interior decoration and material design echoes the deeper truth that we are creatures of structure, that we are shaped by shapes. A protein does its magic not through any moving parts but simply by being folded in a certain way. Life is structured carbon, oxygen, nitrogen, hydrogen, phosphorous, etc. The most essential atomic elements in a living creature are the very things that lie around the universe in greatest abundance. Scattered randomly, these things are just dirt, rocks, dust, random molecules blowing in the wind. Structured, they move, replicate, evolve and eventually assemble complex entities, including scientists.

Crick and Watson didn't discover DNA. But by cracking the structure of DNA, Crick and Watson finally showed how life worked, how biological information is catalogued, copied and distributed. Crick went on to many other dramatic discoveries, figuring out the role of messenger molecules, coming up with the definitive list of amino acids, eradicating once and for all any notion that the traits we acquire as we move through life (say, the ability to throw a football in a tight spiral) can be passed along genetically to our offspring.

Crick and Watson let a genie out of a bottle. It's hard to know where it will lead, this new science of molecular biology, but it is not out of the question that basic phenomena such as aging and death will cease to be inevitabilities and will instead be viewed as pathologies.

Many scientists suspect that DNA exists throughout the universe -- that it's so useful, so naturally emergent from the chemistry of the cosmos, that even alien life would employ this tool for biochemistry. In his book "Life Itself," Crick hypothesized that life on Earth might be the result of panspermia. The term, which hardly seems fit for a family newspaper, refers to a hypothetical civilization's desire to seed the galaxy. Maybe the ancestral microbes arrived on Earth on a crashed spaceship. We could be the offspring of the Klingons.

Crick's idea isn't entirely irrational. Even the simple organisms that existed on Earth 3.5 billion years ago were much more complicated than the nonliving elements around them. DNA is an elaborate molecule. The origin of life is the real missing link of the biological record.

When you happen to be the Crick of Watson-Crick fame you can play around with such fanciful and speculative notions. A visionary is a scientist who no longer has to spend a lot of time in the lab. Crick's long work on the riddle of consciousness was a bit of intellectual indulgence in his later years, like Paul McCartney writing a classical symphony.

Watson has told the story that, when they made their breakthrough, Crick burst into the local pub and told everyone the great news: We found the secret of life! Crick always claimed he couldn't remember doing any such thing.

He was smart enough to know that, for all his achievements, he had not found the meaning of life. The meaning of life is in a totally different category. That's something that each person must investigate in his or her own private laboratory.

By discovering DNA's now-famous double helix structure, Francis Crick cracked the code of life.Francis Crick, left, and James Watson, discoverers of the double-helix structure of DNA, opened the way for the genetic engineering of today.