Happiness is one of the most important parenting goals in today's modern society. To promote a happy childhood, we need to understand what happiness means to children. Contrary to the view that young children may equate happiness with satisfying material desires and experiencing simple pleasures, in this article, I review recent developmental research showing that (1) even young children have a sophisticated understanding about the role of desire satisfaction in happiness, (2) they perceive happiness as contingent on moral goodness, and (3) they experience happiness from performing morally good behaviors. Together, the findings suggest that for children, happiness means more than feeling good about satisfying material desires and experiencing simple pleasures; it also means "being good" to oneself and others. This research deepens our understanding of children's emotional cognition and experience, elucidates the nature and origins of happiness, and has significant implications for fostering a happy childhood and beyond.