Germany is currently among the 10 oldest countries in the world, as measured by the share of population aged 70 years and over. With the baby boomer cohorts of the 1950s and 1960s having started to reach retirement ages, a new phase of ageing is about to take place. In this debate piece, we argue that investments in human capital at any age and at any stage of the life course are indispensable for dealing with an ageing population. Investments in early education are most effective and efficient, as early skills beget later skills. We show that in an ageing society, it is most efficient to invest in children from the very beginning to develop their full human potential, and to ensure that no child is left behind. Moreover, investments in early education programmes have benefits in addition to those directly related to children, including benefits related to fertility, maternal employment and the integration of parents with a migration background. Globally, more and more countries are faced with increasing proportions of older people and decreasing proportions of working-age people in their populations. Thus, what we describe here for Germany can in many respects be transferred to other country contexts.