The committee structure permits members of Congress to study a particular subject intensely. It is neither expected nor possible that a member be an expert on all subject areas before Congress. As time goes by, members develop expertise in particular subjects and their legal aspects. Committees investigate specialized subjects and advise the entire Congress about choices and trade-offs. The choice of specialty may be influenced by the member's constituency, important regional issues, prior background and experience. Senators often choose a different specialty from that of the other senator from their state to prevent overlap. Some committees specialize in running the business of other committees and exert a powerful influence over all legislation; for example, the House Ways and Means Committee has considerable influence over House affairs.