It looks like solid smoke. Or a hologram. When you look at it, the eye has trouble actually focusing on its true shape. It looks. in fact, like a ghost stuff. It's called Aerogel.
Aerogel is a form of nanofoam, an engineered material designed for high strength-to-weight ratio. Based on research from the 1930s by Stanford University's Steven Kistler, this material may soon be the concrete of the future (and a whole lot more). In a 1932 paper published in Nature, Kistler showed that gel is an open structure of a matrix of porous walls with a liquid filling. He reasoned that it could be possible to remove the fluid completely without destroying the structure. The result was areogel.
Aerogel, one of the world’s lightest solids, can withstand a direct blast of 1kg of dynamite and protect against heat from a blowtorch at more than 1,300C. They consist of more than 96 percent air. The remaining four percent is a wispy matrix of silica (silicon dioxide), a principal raw material for glass. Aerogels, consequently, are one of the lightest weight solids ever conceived. (water is actually 300 times denser.) The silica aerogel is an amorphous form of common sand, nonflammable, nontoxic, and environmentally safe.
Mercouri Kanatzidis, a chemistry professor at Northwestern 
University in Evanston, Illinois, said: “It is an amazing material. It has the lowest density of any product known to man, yet at the same time it can do so much. I can see aerogel being used for everything from filtering polluted water to insulating against extreme temperatures and even for jewelry.” Just to give you a rough comparison, one inch of aerogel insulates just as well as ten inches of fiberglass or a window with 10 double panes of glass. The aerogels' extraordinary thermal insulation ability makes them capable of withstanding temperatures in excess of a thousand of degrees Fahrenheit.
Kanatzidis has created a new version of aerogel designed to mop up lead and mercury from water. Other versions are designed to absorb oil spills. In fact, if you handle aerogel for more than a few minutes, you should wear gloves. That’s because aerogel will draw the water out of your skin and leave it scaly and patchy.
It also has green credentials. Aerogel is described by scientists as the “ultimate sponge”, with millions of tiny pores on its surface. In fact, workers are advised to wear clothes when handling aerogel for more than a few minutes as it can draw the water out of skin. This quality also makes it ideal for absorbing pollutants in water.
One of the major problems with areogels has been its brittleness. However, in 2004, University of California scientists working at Los Alamos National Laboratory have recently demonstrated a novel method for chemically modifying and enhancing silica-based aerogels without sacrificing the aerogels unique properties. By mixing metal compounds during the production stage, lab scientist, Kimberly DeFriend showed that areogel's strength can be increased four fold. This allows the aerogels to retain their most valuable porosity and density characteristics while enhancing weaker characteristics like mechanical strength.
http://members.tripod.com/~geobeck/frontier/aerogels.html
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