ArcCatalog tree not displayed

I'm not sure what I did to make this happen but my Catalog tree is not displayed on the left side of ArcCatalog. Normally when one opens ArcCatalog, their screeen may look like this Attachment 20928 however my ArcCatalog now looks like this...Attachment 20929.

Anyone have any ideas how to bring back my Catalog tree?

Thanks in advance! :D

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