In the 1960s, Joseph Altman reported that the adult mammalian brain is capable of generating new neurons. Today it is understood
that some of these neurons are derived from uncommitted cells in the subventricular zone lining the lateral ventricles, and the dentate
gyrus of the hippocampus. The first area generates new neuroblasts which migrate to the olfactory bulb, whereas hippocampal neurogenesis
seems to play roles in particular types of learning and memory. A part of these uncommitted (immature) cells is able to divide
and their progeny can generate all three major cell types of the nervous system: neurons, astrocytes, and oligodendrocytes; these properties
define such cells as neural stem cells. Although the roles of these cells are not yet clear, it is accepted that they affect functions including
olfaction and learning/memory. Experiments with insults to the central nervous system also show that neural stem cells are
quickly mobilized due to injury and in various disorders by proliferating, and migrating to injury sites. This suggests a role of endogenous
neural stem cells in disease. New pools of stem cells are being discovered, suggesting an even more important role for these cells.
To understand these cells and to coax them to contribute to tissue repair it would be very useful to be able to image them in the living organism.
Here we discuss advances in imaging approaches as well as new concepts that emerge from stem cell biology with emphasis on
the interface between imaging and stem cells.