Memory formation is a dynamic process such that each memory changes its content by interacting with distinct, but related experiences. Distinct units of information sometimes interact to generate a new associative memory. Memory is assumed to be stored in the brain as a cellular ensemble consisting of a set of neurons that is activated during learning. Although optical stimulation of a cellular ensemble is known to trigger the retrieval of the corresponding memory, it remains unclear in the cell ensemble level how two distinct memories are integrated to generate an associative memory. Our current findings, using two amygdala-dependent behavioral paradigms, conditioned taste aversion task and auditory cued fear conditioning, suggest in mice that two distinct cell ensembles corresponding to each memory converge to generate an interaction of two distinct memories. Furthermore, in CPFE paradigm with context pre-exposure and immediate shock, activation of a cell ensemble corresponding to two distinct memory events generates an artificial association between initially non-related memory events. The artificial activation of distinct cell ensembles, without any sensory input, is capable of generating an artificially associated memory. Taken together, our finding suggests that the association of distinct units of information is achieved through the synchronous activity of distinct cell ensembles. I will discuss the memory association mechanisms based on these findings.