Most accountings of the millennium's first decade tend to focus on conflict and politics and things that don't work.

Certainly health and science have all those in spades. But there's also been a strong track record in discovery over the last decade, one that can take longer to emerge than the 24-hour news cycle.

Take gene therapy. The hot new tool of the 1990s nearly imploded with the death of a patient in Philadelphia in 1999. But in the last year, advances have eased a form of blindness and pushed the technology to new heights.

The mapping of the human genome was another much-trumpeted advance. Only now, years after its 2003 debut, is its value being realized with insight into the molecular underpinnings of disease.

Not that all developments are good. Patient safety in hospitals remains a work in progress with no easy fix. The health system is too costly with conflicts of interest too prevalent among researchers and pharmaceutical companies.

And even an initial success such as nanotechnology needs to be scrutinized for safety.

Still, health and science represent one of the decade's most dynamic sectors, as these pages show.

Alternative Energy

From its power sources to its cars, the nation got a glimpse of what a post-petroleum world might be like.

"Peak oil" entered the lexicon; petroleum is finite. Officials also are increasingly concerned about global warming emissions related to burning fossil fuels.

So the decade has seen a boom in renewable energy, which in 2008 provided 7 percent of U.S. energy needs.

Solar power, still in its infancy, accounts for just 1 percent of that, but with strong state subsidies, New Jersey ranks second in the nation in solar. Pennsylvania is stronger on wind power, but New Jersey may be first in the nation to have offshore wind farms; three are planned.

For some petroleum substitutes, the road has been rocky. Natural gas is seen as a "bridge" fuel between oil or coal, and is plentiful in Pennsylvania's Marcellus shale formations. But extracting the gas has environmental consequences that officials are still wrestling with.

Perhaps a million of the nation's vehicles now run on alternative fuels, such as 85 percent ethanol, liquefied petroleum gas, compressed natural gas, and hydrogen.

That count doesn't include the hybrid, which uses gasoline and electricity and debuted 10 years ago. There are now 1.55 million gas-electric vehicles on U.S. roads, according to a tally by experts at HybridCars.com

On the horizon is the all-electric car. A few niche models - the Tesla sports car, for instance - are available, and 2010 promises the debut of the Chevy Volt, which can go 40 miles on a charge.

Proponents tout the potential of electric car batteries to act as a vast energy reservoir. They could be charged at night, when demand on the power grid is low, then slowly discharge back into the system during the day, when demand is high.

- Sandy Bauers

Mapping Genomes

A decade ago, the sequencing of the human genome was compared to the moon landing, despite the obvious difference that we all understood what the moon was.

In retrospect, the $3 billion public and private biology project will likely change the world in a more profound way.

The goal was to read the 3 billion "letters" of genetic code written in human DNA. We all carry a slightly different sequence, but scientists thought they could get a sort of reference based on DNA samples from five individuals of various ethnicities.

Scientists officially announced completion in 2000 but continued to work on "difficult" regions for several years. More individuals were added through a project called HapMap - critical for applying the information in the genome to human health.

It's already enhancing medicine, said Hakon Hakonarson, head of the Center for Applied Genomics at Children's Hospital of Philadelphia. Babies now get genetic tests for 20 to 50 diseases in which early intervention can save lives or prevent suffering.

The genome project combined with HapMap has enabled Children's Hospital researchers to find genes linked to type-1 diabetes, asthma, autism, and some childhood cancers.

Identification has helped researchers understand these conditions on a molecular level as well as human pathogens, such as the anthrax spores used in the 2001 attacks and the H1N1 flu that broke out last spring.

- Faye Flam

Nanotechnology

In that overwrought period at the close of the last millennium, writers and pundits predicted that nanotechnology would lead to invisibly small robots that could heal the sick and revive the dead, so long as they were properly frozen. Pessimists worried the same technology would lead to a runaway "gray goo" that would destroy the world.

But nanotechnology "has come from almost nowhere to being one of the dominant technologies people talk about," said Andrew Maynard, chief science adviser of the Woodrow Wilson Center for Scholars.

The term refers to the control and manipulation of matter on the scale of individual molecules, and the use of new "nanomaterials" made from ultrafine particles or ultrathin tubes of carbon.

Without much fanfare, that's changed our world through miniaturization - enabling people to shoot video from a wafer-thin iPod and watch YouTube on a pocket-size phone and do all sorts of other things that would have made James Bond envious back in the 20th century.

Medical researchers are busy working on nanoscale vehicles designed to direct drugs where they're needed - to a malignant tumor, for example. Others are designing invisibly small devices aimed at regrowing nerves.

And while the gray goo nightmare probably belongs in science fiction, concerns have emerged as scientists realize that these new types of materials have extremely novel properties and may act in unexpected ways in the body.

- Faye Flam

On Beyond Pluto

In planetary science, the '00s were bad for traditionalists. By mid-decade, a sharper generation of telescopes had shown a bevy of new worlds onbeyond Pluto.

The former ninth planet had always been a misfit - tiny, distant, and moving in a widely oblong orbit. The last decade has shown our solar system's rebel was part of its own disorderly gang. First came Quaoar, then Sedna, then 2003UB313, dubbed "Xena," which is three times Pluto's size.

Astronomers realized they would have to accept hundreds of planets or reclassify Pluto as part of a group of similar icy bodies orbiting in the Kuiper Belt.

Learned committees decided that Pluto was not a planet but a Kuiper Belt object. That unleashed a wave of outrage not seen since Earth was demoted to planet from center-of-the-universe.

Astronomer Neil Tyson suggested that children were upset because they associate Pluto the former planet with Pluto the Disney dog.

- Faye Flam

Stem Cells

For much of the decade, the fledgling field of "regenerative medicine" was hamstrung in the United States by the ethical debate over destroying embryos to harvest their wondrous stem cells.

Then came a breakthrough. In November 2007, ordinary skin cells were reprogrammed to behave like embryonic stem cells - reproducing indefinitely and spinning off all human cell types.

These "induced pluripotent stem" (IPS) cells have become a valuable tool for modeling diseases. At the University of Wisconsin, for example, IPS cells made from a child with spinal muscular atrophy have been used to study the disorder and screen possible drug treatments.

Scientists recently removed a safety obstacle, resetting IPS cells' developmental clocks without using methods that could cause genetic mutations. But other concerns have arisen. "What we're seeing is that IPS cells routinely have chromosomal problems," said John Gearhart, director of the University of Pennsylvania's Institute for Regenerative Medicine.

He believes the next advance will involve reprograming a specialized cell to become a related cell type - say, turn a pancreatic cell that makes digestive enzymes into one that secretes insulin. Harvard researchers have already done just that in mice.

Embryonic stem cell research, meanwhile, is enjoying a resurgence in the United States, due to President Obama's decision early this yearto lift his predecessor's restriction on federal funding for the work.
- Marie McCullough

Pandemic Flu

The first pandemic of the 21st century arrived with a bang (remember Mexico?) then went out with a bust (have youbeen vaccinated?).

Swine flu has already killed about 10,000 Americans. But that's not out of line for half a flu season. Not yet, anyway.

It was the second time this decade that the boys and girls of public health cried wolf. The killer bird flu (starting circa 2004) cannot spread easily from person to person. Not yet, anyway.

The vast potential of the influenza virus - avian varieties are fatal in half the cases - combined with the limited ability of modern medicine to contain it is what scares experts.

Tamiflu doesn't do much against any kind of flu. Vaccine is still grown, often slowly, in chicken eggs. And drug firms seem to lack the capacity to make enough pandemic and seasonal flu vaccine.

Many scientists believe a really bad pandemic is coming. But for now, said Vanderbilt University vaccinologist Kathryn Edwards, "we are pretty lucky this is the one we got."

- Don Sapatkin

Gene Therapy

For as long as scientists have known that some diseases are caused by genetic mutations, the dream has been to correct these biological misspellingsmistakes and cure the patient.

After some early false starts and at least one severe misstep, the dream of gene therapy is coming closer.

In 2008, three teams of researchers improved the eyesight of patients suffering from a rare form of blindness. One trial took place at Children's Hospital of Philadelphia; that trial, along with one of the others, also had ties to the University of Pennsylvania.

This year, another group reported it had arrested the progression of the rare brain disease featured in the movie Lorenzo's Oil - called adrenoleukodystrophy. Still other scientists have tackled rare immune-system disorders and Parkinson's disease.

The corrective genes are delivered to patients via disabled viruses - some injected into the body, others delivered to bone marrow that has been removed from the patient. The advances have come as scientists learn which viruses to use and how best to tweak them.

That some of the recent success came at Penn marks a full circle of sorts since it was there that gene-therapy patient Jesse Gelsinger died after being treated in 1999. The young field seems on a more promising course.

- Tom Avril

Loss of Species

The Earth is thought to have endured five mass extinctions in its history, with large numbers of animals and plants disappearing for reasons that range from asteroids to climate change.

Many scientists believe that number six is now under way, and that this time a key culprit is humans.

Habitat destruction, overfishing, and the emission of heat-trapping greenhouse gases have all been blamed.

Frogs, salamanders, and other amphibians are bearing some of the heaviest losses thus far. Besides the impact of humans, scientists discovered in 2001 that a fungal disease - chytridiomycosis - was wreaking havoc.

Any loss of species is of concern. The disappearance of one creature can cause a dangerous ripple effect, leading other species to perish or thrive, depending on whether they ate - or were eaten by - the one that went extinct.

In one arena, the impact of humans is very direct: fisheries. If we catch too many, there aren't enough left to sustain the population.

This year, 21 researchers reported a bit of good news in the journal Science. Carefully managed fisheries showed signs of recovery, including in parts of the United States, Iceland, and New Zealand. But of all the fish stocks that were studied, 63 percent still needed to be rebuilt. And the authors warned that overfishing may simply have been displaced to countries with weak regulation and enforcement.

- Tom Avril

Toxic Substances

Concerns have mounted over many chemicals common in household products.

Bisphenol A and phthalates have come under scrutiny because they are believed to have hormone-disrupting properties and can lead to serious health effects.

Bisphenol A - also called BPA - is found in many hard, clear plastics, such as reusable food containers, and the lining of food cans. Phthalates also are in dozens of consumer products from deodorants to shower curtains.

PBDEs, which are flame-retardants used in electronics, foam and fabrics, are suspected of causing liver and thyroid toxicity and neurodevelopmental toxicity. On Dec. 17, the two major U.S. producers announced commitments to phase out one of its forms by Dec. 31, 2012.

Earlier this month, Environmental Protection Agency administrator Lisa P. Jackson told a legislative hearing on the Toxic Substances Control Act that the public "is turning to government for assurance" have been assessed using the best available science, "and that unacceptable risks have been eliminated."

"But, under existing law," she said, "we cannot give that assurance."

- Sandy Bauers

Patient Safety

Ten years ago, the Institute of Medicine issued its landmark To Err Is Human report, launching a movement to reduce medical errors that killed an estimated 98,000 patients a year while adding billions of dollars in costs.

As a result, doctor's offices increasingly are computerizing prescriptions, and the federal government no longer pays hospitals for some care necessitated by mistakes.

Pennsylvania was the first state in the nation to require hospitals to report and disclose how many patients contracted infections during care each year. Both Pennsylvania and New Jersey are among the first states to require hospitals to report medical errors to regulators, though not to the public.

Still, malpractice worries and medical culture keep many from admitting mistakes. Progress has been slow, said David Nash, dean of the school of population health at Thomas Jefferson University.

"I would give us a C+," Nash said of all health care. "It is not something we can throw a switch and make it go away."

- Josh Goldstein

Heart Stents

The treatment of clogged heart arteries changed dramatically in the last decade.

A new type of coronary stent - tiny wire scaffolds used to prop open clogged heart arteries - put a crimp in the bypass business even as new techniques such as minimally invasive surgery, so-called off-pump and hybrid procedures, were developed and matured.

In April 2003, the U.S. Food and Drug Administration approved the first drug-eluting heart stent. The device was thought to be a major advance over bare-metal stents because it was coated with medicine to reduce scarring, a major reason that 15 percent to 30 percent of patients' arteries clogged again and needed more procedures.

Now the new stents are being used with surgery to comprehensively treat heart patients through small incisions in the chest that do not require open heart surgery, said Francis P. Sutter, chief of cardiac surgery at Lankenau Hospital in Wynnewood, Pa. Moreover, patients can also get the combined procedure without being put on a heart-lung machine, known as off-pump.

"The things that we are doing now, back when I was starting, people said no way," Sutter said. "It is great for the patients. It is a very exciting time."

- Josh Goldstein