Telomeres are protective caps on DNA that shorten as we grow older. Now, one of the first studies to examine telomere length (TL) in childhood finds that the initial setting of TL during prenatal development and in the first years of life may determine one’s TL throughout childhood and potentially even into adulthood or older age. The study also finds that TL decreases most rapidly from birth to age 3, followed by a period of maintenance into the pre-puberty period, although it was sometimes seen to lengthen.