After Attorney General Jeff Sessions recused himself from the investigation for failing to disclose his private meetings with Russian Ambassador Sergey Kislyak, Deputy Attorney General Rosenstein took charge and appointed Robert S. Mueller III as special counsel on May 17. That was about a week after President Trump fired FBI Director James B. Comey. Though Mueller has a large degree of independence, Rosenstein oversees the investigation. He approves the special counsel’s budget and any expansion of the special counsel’s investigation.

Generally the FBI investigates crimes and the Justice Department prosecutes them.

Here is a breakdown: