  Flavor effects can have a significant impact on the final estimate of the
lepton (and therefore baryon) asymmetry in scenarios of leptogenesis. It is
therefore necessary to account fully for this flavor dynamics in the relevant
transport equations that describe the production (and washout) of the
asymmetry. Doing so can both open up and restrict viable regions of parameter
space relative to the predictions of more approximate calculations. In this
review, we identify the regimes in which flavor effects can be relevant and
illustrate their impact in a number of phenomenological models. These include
type I and type II seesaw embeddings, and low-scale resonant scenarios. In
addition, we provide an overview of the semi-classical and field-theoretic
methods that have been developed to capture flavor effects in a consistent way.
