The DNA sequence of Tetrahymena telomeres was the first to be determined among all telomeres by Elizabeth Blackburn and Joseph Gall in 1978. In 1982, Jack Szostak and Blackburn showed that the unique DNA sequence contained in the telomeres served to protect the chromosomes from degradation. In 1985, Carol Greider and Blackburn showed how the telomeres could be elongated by the enzyme telomerase. These discoveries are milestones marking the start of the molecular era of telomere biology. Telomeres occur at the ends of chromosomes, like the plastic sheaths at the ends of shoelaces. The significance of telomere research was recognized by the award of the Nobel Prize in Physiology or Medicine to Blackburn, Szostak, and Greider in 2009.

Although the award of the Nobel Prize is undoubtedly one of the most exciting events in the history of telomere biology, it by no means signals that we have reached the peak of telomere research. Research on telomeres and telomerase is still moving at a very rapid pace, and new findings about telomere functions and the underlying mechanisms are unveiled daily. This paper reviews the early work as well as recent advances in the field.