This chapter advocates that developmental science is well positioned to engage in systematic investigation that creates taxonomy of family environments with the explicit goal of understanding how different types of family environments contribute to the lifelong development of individual children. Within a family, at least three levels of analysis are possible: analysis at the level of individuals, analysis at the level of social subunits, and analysis at the level of the group as a whole. Family behavior is expected to change over time and across situations, as a direct result of shifts in the family's goals, strategies and plans, resources, and individual experiences of its members relative to the six functional domains. Family success in a general way is determined by how well a family functions relative to achieving family goals. The family goals used in judging success may be identified either by family members or by external sources.