The passage describes the physiological process of puberty. It states that between early childhood and ages 8-9, the hypothalamic-pituitary-gonadal axis is dormant with undetectable sex hormones. Starting 1-3 years before puberty, low levels of LH during sleep can be detected, reflecting increasing pulsatile secretion of GnRH from the hypothalamus. This pulsatile secretion of gonadotropins causes the enlargement and maturation of the gonads and the production of sex hormones, culminating in the appearance of secondary sex characteristics at the start of puberty. Genetic and environmental factors like nutrition and activity levels can affect the timing of puberty's onset.