Over the past decade it has become increasingly clear that stochasticity, or luck, plays a large role in the life history trajectories individuals experience. Some individuals live long lives, others die young; some individuals will produce many offspring, whereas others are not so lucky. When individuals are identical in their probabilities of growth, survival and/or reproduction (as they are in many demographic models), the results of their life history, such as their longevity and lifetime reproductive output, will vary due to luck. When individuals are heterogeneous in their vital rates throughout life, for example due to trait variation, this generates additional variance in the fates of individuals. Such differences in individual fates, whether they are due to luck or heterogeneity, can affect both the ecological fate and the evolutionary fate of the population. There now exist several methods aimed at quantifying or partitioning the relative contributions of luck and heterogeneity to the variance in individual fates. In this organized oral session, we will present an overview of the theories and methods that exist with respect to quantifying variability in individual fates; we will relate the concepts of luck and heterogeneity to questions of heritable trait variation; and we will illustrate what its impacts are through meta-analysis and case studies. The goal of this organized oral session is to introduce the methodologies for analyzing the impacts of luck and heterogeneity in life histories to a broad audience and provide an introduction to studies where such analysis has proven important. In particular, we hope to introduce empirical ecologists to the debate on the sources of variation in life history trajectories: whether such variation is the result of stochasticity that naturally arises from probabilistic life history events or if it is the emergent result of genuine differences in vital rates due to heterogeneous factors (some of which are unobserved).