Memory consolidation and reconsolidation reflect molecular, cellular and systems-level processes that convert labile memory representations into more permanent ones, available for continued reactivation and recall over extended periods of time. Here, we discuss the complexities of consolidation and reconsolidation, and suggest they should be viewed not as all-or-none phenomena, but as a continuing series of biological adjustments that enhance both the efficiency and the utility of stored memories over time and in response to changing needs of the organism. As such, consolidation and reconsolidation might be better thought of as memory organization and reorganization. A rapidly growing body of evidence suggests that many of these processes are optimally engaged during sleep.