The Code of Federal Regulations (C.F.R.) is the codification of rules created by the departments and agencies of the Federal Government. It is divided into 50 titles that represent broad areas subject to federal regulation. The 50 subject titles of the regulations in the C.F.R. are similar but not identical to the titles of the federal statutes in the U.S. Code.
Here is an example of a regulation in the C.F.R.
21 C.F.R. § 110.110
The first number is the title number, letting you know the general subject area of the regulation.
Title 21 - Food and Drugs
The second number is the part and section number, separated by a period.
The C.F.R. is available via the following databases and websites: