Telomeres are very important structures that protect chromosomal ends from recombination, but the structure itself induces irreversible reduction without the presence of telomerase activity. Researchers are now collecting evidence of telomere dynamics in clinical samples, but we are still far from being able to discuss telomere dynamics and chromosomal changes in such materials. Although there is a growing body of evidence that telomerase might be a very important key enzyme to obtain immortality, and possibly oncogenesis, other pathways for immortal characteristics are currently being reported. Moreover, we do not have any evidence at hand to indicate whether quiescent cells, especially most primitive stem cells, have telomerase activity or not (67 –73 ).