Shinya Yamanaka / Department of Stem Cell Biology / AP
Human induced pluripotent stem cells, or iPS cells.
Embryonic stem cells displayed in laboratory vials
Darren Hauck / Getty
A colony of human embryonic stem cells is seen on a computer monitor at the University of Wisconsin–Madison
Darren Hauck / Getty Images
Kejin Hu, a research associate, removes a colony of stem cells from an incubator to look at them under a microscope at the Wisconsin National Primate Research Center at the University of Wisconsin–Madison on March 10, 2009
RNL Bio / AFP / Getty Images
Two puppies cloned through fat stem cells from a Beagle, shown in January 2009
COLD CURE: Stem cells come out of cryostorage at ReNeuron's labs
ILLUSTRATION BY LON TWEETEN FOR TIME
New treatments are under development to zero in on cancer stem cells specifically, which today's methods can not do
ADVANCED CELL TECHNOLOGY / AP
A single cell is removed from a human embryo to be used in generating embryonic stem cells for scientific research.