From Scientific American:
Stem cells can transform into whatever cell the body tells them to. Unfortunately, scientists have yet to master that particular gift of gab. But investigators at Stanford University may soon crack the language with tiny “chat rooms” for stem cells. In their natural milieu, stem cells have a variety of neighbors that pass on chemical messages at exact spots at particular times in specific amounts to guide the cells’ development into a given cell type. In today’s laboratory, however, researchers often bathe the whole cell with chemicals–kind of like out-of-control beer keggers compared with the sophisticated cocktail parties the body normally throws for stem cells. To uncover the mostly unknown placement, timing and identity of the cues, Stanford materials scientist Nicholas A. Melosh and his colleagues are re-creating the niche where stem cells normally dwell. They are developing a microscopic lab on a silicon chip that surrounds a stem cell with as many as 1,000 cavities, each 500 nanometers wide.
More here.