In this special issue we commemorate theoretical biologist Alexey Olovnikov (1936-2022), whose theory of marginotomy has laid the foundation for the new field of biology that studies the molecular structure of telomeres and its role in health, longevity and aging. This issue contains a collection of reviews and research articles that discuss different aspects of telomere and telomerase research, ranging from telomere length dynamics in wild animal populations to problems of telomere maintenance during human space flight.