Informal communication, e.g., unplanned "water-cooler" conversations, has been suggested to play important roles in collaborative work and organizational innovation. It provides opportunities among employees for exchanging work-relevant information, initiating potential collaboration, maintaining awareness of workplace context; and supports social functions such as transmission of office culture and maintenance of common ground and a feeling of connectedness between co-workers. (Johnson, Donohue, Atkin, & Johnson, 1994; Kraut, Fish, Root, & Chalfonte, 1993; Nardi, 2005; Whittaker, Frohlich, & Daly-Jones, 1994). Even as Computer-Mediated Communication (e.g., through phone, IM, emails) has extended our capability of communicating with colleagues and co-workers across distance and time, people continue to suffer from a lack of informal communication in today.s computermediated distributed work, especially with colleagues outside their daily work circles (Perlow, 1999). Researchers and practitioners have been seeking ways to simulate catching-up interactions within the space of computer-mediated communication. However, the best ways to support informal communication among co-workers across walls and geo-locations, still remains as an open and challenging research problem. Microblogs, a relatively new phenomenon, provide a communication channel for people to broadcast information that they likely would not share otherwise using existing channels such as email, phone, IM, or blogs. Microblogging has become popular quite quickly, raising its potential for serving as a new informal communication medium at work, providing a variety of impacts on collaborative work (e.g., enhancing information sharing, building common ground, and sustaining a feeling of connectedness among colleagues). The exploratory research reported in this dissertation aims at first obtaining a baseline understanding of why people choose to microblog and as part of that, to characterize the technology affordances of microblogging. It continues an exploratory research path by exploring the perceived impacts of microblogging as a means for informal communication in the workplace, summarizing these observations as opportunities and challenges that are presented by microblogging as an aid to informal communication. Scenario-based design (Carroll, 2000; Rosson & Carroll, 2002) is adopted in the final phase of the dissertation, where in I synthesize scenarios, tradeoffs and themes from the field studies and use these to guide the design, prototyping and evaluation of a novel microblogging system GroupBuzz. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]