As a guide to what’s next in the Trump-Russia investigations, former FBI director James Comey’s testimony on the Hill was remarkable mostly for what was not said — and what can be inferred from it.

Comey declined to answer several questions from senators in Thursday’s Intelligence Committee hearing, saying that they touched on matters relating to ongoing investigations or classified material. He did say he could discuss them with lawmakers in closed session. Those evasions, and the manner in which Comey delivered them, show a broadening of an investigation into the Russian campaign to influence the 2016 election and whether it involved people connected to Donald Trump or the president himself.

So what can’t Comey talk about? Here’s a short list, and why the questions matter.

1. Why did Attorney General Jeff Sessions recuse himself from the Russian investigation and why did “career people” in the Department of Justice know about it weeks in advance?

Comey: “We were aware of facts that I can’t discuss in an open setting that would make his continued engagement in a Russia-related investigation problematic…The career people were recommending that he recuse himself,” not just from the specific investigation but also “Russia-related matters.”

Why it matters: Questions from Sen. Kamala Harris, D-Calif., suggest that the intelligence committee will be playing close attention to how well Sessions holds to that recusal pledge. Also, the fact that Comey can’t discuss related to what Sessions knew and how he interacted with members of the Russian government might have relevance to the investigators. Sessions has also reportedly offered to resign, but the offer was rejected by Trump. After the hearing reports surfaced that, in closed session, Comey told lawmakers about a third, undisclosed meeting between Sessions and Russian officials.

2. Was there an attempt to set up a secret Trump transition team-Russia channel, safe from the prying eyes of the U.S. intelligence community? It’s a story that’s been widely reported and linked to Trump’s son-in-law and advisor Jared Kushner.

Comey refused to publicly comment “on whether that happened.”

Why it matters: there are plenty of good reasons why the White House should not have a special communication line to Russia beyond normal diplomatic channels. Today, Comey offered a reason rooted in simple operational security: “The primary risk is obvious: you spare the Russians the cost and effort of having to break into our communication channels by using theirs.”

3. Is the FBI still trying to corroborate portions of the explosive “Steele Dossier?” (Compiled by a former British spy, this is the list of allegations about Trump’s ties to Russia, including the names of Russian spies working in the United States, charges that Trump owed money to a host of Russian oligarchs, and suggestions that the Kremlin has video of Trump in a sexually compromising situation.)

Comey: “It’s Director [Robert] Mueller’s job” to discuss that. But the former FBI chief did reveal that Trump had called him twice to push back on the Dossier’s most salacious allegations.

Why it matters: some media reports have indicated that the FBI has corroborated portions of the dossier but exactly which ones remains a mystery. (The Bureau has offered no official comment about any verification.) One detail that’s reportedly been borne out by British intelligence agents is that Russian diplomat Mikhail Kalugin participated in election interference activities in Washington before departing back to Russia last August. (Kalugin denies the charge.) If any of the dossier’s allegations about Trump turn out to be true, that would mean that the Kremlin potentially had blackmail material — or to borrow the Russian phrase, kompromat — to use against him.

4. How are members of the Trump campaign or staff connected to Vnesheconombank, or VEB, the state-controlled bank that’s been called a tool of Russian “soft power” and influence peddling?

Comey: Asked what he knew about the bank, he answered, “Nothing I can talk about in an open setting.”

Why it matters: VEB is a subject of U.S. sanctions. Kushner reportedly met with the bank’s CEO, Sergey Gorkov, in December. Some reports indicate that he may have omitted that meeting on forms he filled out to gain a security clearance. The Wall Street Journal has reported that the bank helped to finance a Trump hotel project in Toronto.

5. Does Comey believe Donald Trump colluded with the Russian government?

HIs answer: “It’s a question I don’t think I should answer in an open setting.” He also sad that he was not trying to “suggest by my answer something nefarious.”

He furthered offered that when he left the FBI, there was no investigation into Trump directly — but that the question of collusion “will be answered by the investigation, I think.”