The real work of lawmaking happens in the legislative committees. One of the reasons for the committee system is division of labor. The American system of specialized standing committees allows members of Congress to build up expertise in issue areas as they build up seniority in Congress. Standing committees are broken down into subcommittees that allow members to acquire even more specialized expertise. Subcommittee members are often the dominant forces shaping legislation. In addition to their work on standing committees, members of Congress serve on joint committees made up of legislators from both houses; select committees established to deal with special issues; and conference committees, which work out differences between versions of legislation passed by the two houses. Leadership on committees is linked to seniority (although members have the option of secret ballot).
Committee hearings represent an important stage in drafting legislation and are often used by legislators as ways of gaining publicity on an issue. Committees themselves differ in terms of style. Some work by consensus; others are more conflictive.