After being introduced, a bill is referred to the appropriate committee for review.
There are 17 Senate committees, with 70 subcommittees, and 23 House committees, with 104 subcommittees. The committees are not set in stone, but change in number and form with each new Congress as required for the efficient consideration of legislation.
Each committee oversees a specific policy area, and the subcommittees take on more specialized policy areas. For example, the House Committee on Ways and Means includes subcommittees on Social Security and Trade.