OSHA is one federal agency. It is not made up of other federal agencies. I does have sub-organizations within it, which are called Directorates, and Offices.
Government offices, agencies, and departments make up the bureaucracy.
All of the above: Congress, EPA, EU
Departments
Departments
Congress and government agencies make up the legislative branch
Administrative law or regulatory law. The various federal executive agencies promulgate the various regulations that make up the Code of Federal Regulations. State agencies make their own administrative codes as well.
Many different agencies have many different requirements to join their organization, however if you look up your specific company, their homepage should tell you all you need to know.
There are way more than three agencies! Perhaps you're thinking of the three branches of federal govenment: Legislative, Executive and Judicial.
the legislative branch is made of the congress agencies and the goverment agencies
NCHS and CMS
"Alphabet agencies" were created by Franklin Roosevelt to combat the effects of the Depression. The agencies did not end the Depression. However, they provided useful work to many people and constructed numerous public works, such as libraries and dams, many of which are still in use.