Temporarily holding information in mind is an important part of many cognitive processes. For example, when listening to a story, you have to maintain multiple pieces of information in mind in order to comprehend what the story means. Working memory is the mental workspace that is used to temporarily maintain and manipulate this kind of information. A central question in cognitive neuroscience is how this working memory system functions. In this dissertation, I use novel behavioral, neural, and computational methods to address this question and to expand our understanding of working memory theory. In Chapter 1, I provide evidence that maintaining information in working memory relies on multiple sub-processes, including storage capacity and attentional control. In Chapter 2, I characterize the multi-faceted nature of working memory by dissociating two distinct delay period signatures of working memory, the contralateral delay activity (CDA) and lateralized alpha power. In Chapters 3 and 4, I ask how these two delay period signatures of working memory respond to interruptions in order to further delineate their temporal dynamics. Finally, in Chapter 5, I build a model using delay period activity to predict individual differences in the amount of information someone can hold in working memory. Taken together, this research informs contemporary theories of working memory, supporting a working memory system that is comprised of multiple sub-component processes.