Figure 1: Screen shot of Themail showing a user’s email exchange with a friend during 18 months. We present Themail, a visualization that portrays relationships using the interaction histories preserved in email archives. Using the content of exchanged messages, it shows the words that characterize one’s correspondence with an individual and how they change over the period of the relationship. This paper describes the interface and content-parsing algorithms in Themail. It also presents the results from a user study where two main interaction modes with the visualization emerged: exploration of “big picture ” trends and themes in email (haystack mode) and more detail-oriented exploration Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee.