The amount of information we can actively maintain 'in mind' is very limited. This capacity limitation, known as working memory (WM) capacity, has been of great interest because of its wide scope influence on the variety of intellectual abilities. Recently, there has been an ongoing debate about how this capacity should be best characterized. One viewpoint argues that WM capacity is allocated in a discrete fashion with an upper limit of three to four representations. An alternative viewpoint argues that the capacity can be allocated in a continuous fashion with no upper limit in the number of representations. In this article, we will review recent neurobiological and behavioral evidence that has helped shape the debate regarding one of the more central mechanisms in cognitive neuroscience.