The present invention provides a user interface that includes a first column for chronologically displaying a set of messages (objects) in a conversation, and a second column for displaying a branch of messages (objects) corresponding to a message (object) selected in the first column. The user interface further includes, among other things, a list of participants to the conversation, a vertical index (time line), a list of related conversations and a conversation map that illustrates a hierarchy of the conversation. Each message (object) in the first column can have an associated indicator for indicating a quantity of predecessors and successors to the set of messages (objects), as well as an in-line reply button for replying to the set of messages. Each of the messages displayed of the second column can have one or more associated navigation buttons for navigating adjacent hierarchical levels.