Divergent cultural, religious, and ideological beliefs and practices are often challenging to contemplate and difficult to accept when they conflict with an individual's own convictions and way of life. The recognition that children and adolescents grow up in an increasingly diverse world has led to a general interest in fostering tolerance. In this article, we discuss three central questions on tolerance and related research. First, we consider age-related patterns of responses toward tolerance of diversity and whether they depend on the type of dissenting beliefs and practices children are asked to tolerate. Second, we focus on how and why children are asked to be tolerant. Third, we discuss the boundaries of tolerance--the reasons and conditions that make tolerance less likely. Overall, we conclude that tolerance and intolerance can occur at all ages and depend on what, how, why, and when individuals are asked to tolerate belief discrepancy and dissenting practices.