CLARITY BRAIN IMAGING
This year, researchers invented a new way of imaging the brain which many say will fundamentally change the way labs study the intricate organ. CLARITY, a method of rendering brain tissue transparent, removes the biggest obstacle to traditional brain imaging: the fatty, light-scattering molecules, called lipids, which form cellular membranes. By replacing lipids with single molecules of a clear gel, the technique renders brain tissue transparent while leaving all neurons, other brain cells and their organelles intact. This allows researchers to infiltrate the brain with labels for specific cell types, neurotransmitters, or proteins, wash them out, and image the brain again with different labels - a process they say could speed up by a hundredfold tasks such as counting all the neurons in a given brain region.
CLONING HUMAN STEM CELLS
After more than a decade of failures, researchers announced they had derived stem cells from cloned human embryos. Such cells can develop into any of the body's cell types, and researchers hope to use them to study and treat diseases. Mice, pigs, dogs and other animals have been cloned by the same technique used on Dolly the sheep, but human cells have proved much trickier to work with. This year a new recipe - including a dash of caffeine, which appears to stabilize key molecules in delicate human egg cells - solved the problem. Now researchers must determine how embryonic stem (ES) cells from the cloned embryos stack up against induced pluripotent stem (iPS) cells, which behave much like ES cells but are not derived from human oocytes or embryos
In theory, pluripotent stem cells have the ability to become any type of cells in the body, but coaxing the cells to grow into specific tissues is still a challenge. This year, researchers made remarkable progress by growing "organoids" - liver buds, mini-kidneys and even rudimentary human brains - in the lab. Although the brains have no blood supply and stop growing when they reach the size of an apple seed, their tissue and structure are surprisingly similar to those of developing human brains. Researchers have already used them to gain new insights into microcephaly, a condition in which the brain doesn't grow to its full size.
COSMIC PARTICLE ACCELERATOR IDENTIFIED
Cosmic rays - high-energy protons and other particles from outer space - were first detected 100 years ago. Now researchers have finally nailed down solid evidence of where they come from. Theorists had long suspected that most are accelerated in the shock waves from massive exploding stars, or supernovae. If so, they reasoned, some of the particles must collide with atoms in space to produce subatomic particles called pions, which would then decay into gamma rays. This year the Fermi Gamma-Ray Space Telescope spotted the telltale pion-decay signature in the debris from two supernovae.
IMPROVED VACCINE DESIGN
Researchers have long hoped that structural biology, the study of the molecules of life, would help them design better vaccines. This year, it began to deliver. After crystallizing and analyzing an antibody the body uses to combat respiratory syncytial virus (RSV) infections, which hospitalize millions of infants each year, scientists designed an immunogen (the main ingredient of a vaccine) that overnight became a leading candidate in the race to develop an RSV vaccine. Experts say this is the first time structural biology has clearly led to such a powerful immunogen. Other researchers are now harnessing the same tools in efforts to develop new HIV drugs.
NEWCOMER JUICES UP THE RACE TO HARNESS SUNLIGHT
A new breed of materials for solar cells burst into the limelight this year. Known as perovskites, they are cheap, easy to make, and already capable of converting 15 percent of the energy in sunlight to electricity. While that remains below the efficiency of commercial silicon solar cells, perovskites are improving fast. one particularly promising feature is that they can be layered on top of silicon solar-cell material to harness a range of wavelengths that neither could capture alone.