Abstract Coral bleaching is one of the most studied phenomena associated with coral reefs. In the broadest sense, it is described as a color change that occurs in response to a range of stres- sors. Coral bleaching has affected coral reefs in recent mass bleaching events which are due to episodes of warmer than normal sea temperature. These changes are linked to climate change and are exacerbated by light and to a lesser extent by flow and other stres- sors on coral reefs. While some of the details still remain to be filled in, the Photoinhibition Model of coral bleaching goes a long way to explaining why reef-building corals bleach, although the precise point of lesion during the initial steps remains debatable. Some cau- tion is needed in terms of technology affecting our conclusion as to whether the host or the symbionts (or both) are the most critical element in mass bleaching episodes. Evidence for consistent physiological differences between the clades of Symbiodiniltm remains elusive, as does evidence of the ecological flexibility of symbiosis to changing environmental con- ditions. While "shuffling" [sensu Baker, 2003] of symbionts indeed occurs, major changes that result in evolutionarily novel symbionts (evolutionary "switching") are rare and do not occur at ecological meaningful time scales. Furthermore, it is not a forgone conclusion that space needs to be created within the coral house in order for "shuffling" to occur, and hence the link between bleaching and shuffling is somewhat tenuous.