Chapter 2 delves into the critical role of congressional hearings and witnesses during the committee stage, emphasizing their significance in shaping legislative outcomes and policy formulation. It explores how hearings serve as one of the prime avenues for information gathering, drawing from previous studies to highlight their impact on communication among legislators, interest groups, and bureaucrats. The chapter unpacks the intricate process of selecting witnesses, elucidating the process of inviting individuals who provide members of Congress information during the committee stage. It underscores the choices and variables present in this selection process – such as expertise, ideological leaning, and organizational affiliations. Ultimately, this chapter serves as a comprehensive primer on the process of witness selection for congressional hearings and describes the pivotal role played by witnesses in a key stage of policymaking.