"I don't think the human race will survive the next 1,000 years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars."

So said cosmologist Stephen Hawking last year. Optimist or not, it is clear there are many formidable hurdles to clear before we will be able to live for extended periods away from Earth. It may take centuries before we have truly colonized space, but the prospect -- especially after the Space Shuttle Atlantis returned to Earth last week -- no longer belongs to science fiction.

A fundamental challenge is to find a way of growing food in space. When Atlantis touched down, it carried with it seedpods from soybeans that had been planted and nurtured, which then germinated, developed into plants and flowered -- all in space. It is the first time that a major crop has completed its growth cycle, from planting seeds to growing new seeds, in space. Space poses huge and unique challenges to biotechnicians. Can a seed germinate and grow properly in microgravity? How can water and nutrients be delivered to a plant in conditions of weightlessness? Will genes that evolved over millions of years on Earth work properly in space? Previous experiments have been described as "crude."