Abstract: Human neurological disorders and spinal cord injuries are caused by a loss of neurons and glial cells in the brain or spinal cord. The proof-of-principle of cell therapy is that replacing damaged cells with new healthy ones will restore the lost function. Isolating and manipulating autologous neural stem cells (NSCs) could provide an ideal source of cells for use in cell replacement and the transfer of genes to a diseased central nervous system. NSCs are immature cells present, not only during embryonic development, but also in the adult brain of all mammalian species, including humans. The presence of NSCs in the adult mammalian brain has been described in two neurogenic niches, the ventricular-subventricular zone (V-SVZ) of the anterolateral ventricle wall and the subgranular zone of the hippocampal dentate gyrus. Typically, NSCs are defined as self-renewing multipotent cells that can generate neurons, astrocytes and oligodendrocytes. The major barrier to isolating adult NSCs in humans is the inaccessibility of living tissue. For this reason, an enormous effort has been made to derive neurons from human adult stem cells isolated from various tissue sources.