Scientists have used embryonic stem cells to generate blood -- a feat that could eventually lead to endless supplies of type O-negative blood, a rare blood type prized by doctors for its versatility.

"We literally generated whole tubes in the lab, from scratch," said Robert Lanza, chief science officer at Advanced Cell Technologies.

People usually require blood transfusions that match their own blood type: A mismatch can be fatal. Type O-negative can be safely transferred into anyone, but is only possessed by about 7 percent of the population, leaving supplies perpetually short.

The new technique, devised by Lanza and colleagues at the Mayo Clinic and University of Illinois, is still preliminary. Its safety hasn't yet been proved in animals, much less humans.

In its name is the essay’s difference: where other literary modes–novel, poem, play–succeed or fail, the essay, by definition, tries. Too short to be definitive on any topic, the essay can’t manage the comprehensive. It aspires to adequacy, fluency. An essay can argue well, to be sure, but usually argues best for itself and for it’s writer’s best self. “I am myself the matter of my own book,” the namer of the essay said at the beginning of his book of 107 attempts, better and worse, at defining the form.

A small, speckled, asparagus-green chameleon of Madagascar, by contrast, holds a world speed record among just about all of the nearly 30,000 different animals equipped with four limbs and a backbone.

Millions of people are deciphering vintage texts without knowing it - and forging a new path for computing.

It’s hard to imagine an ecosystem better protected by nature — and man — than the Galápagos Islands. They lie some 600 miles off the coast of Ecuador. Most of the land is included in a national park, and the waters surrounding the islands form one of the largest marine protected areas in the world. The Galápagos Islands have often been portrayed as an evolutionary laboratory, which is how Darwin came to understand them after stopping there in 1835. But in recent years, the islands have become a laboratory for conservation — an ongoing experiment in how to preserve a nearly intact ecosystem while still making it available to tourists.