A landmark discovery by researchers at McMaster University could radically alter the way scientists can use embryonic stem cells to grow replacement tissues and treat cancer.

The study found that human embryonic stem cells build themselves a nurturing cocoon that feeds them and directs their ability to transform into other types of tissues.

By manipulating the products of this tiny, cellular placenta, it may be possible for scientists to prompt the stem cells to grow into desired tissues and organs, or to switch off tumor growth in cancers.