5 key takeaways from Robert Mueller's testimony

The big day is underway. After months of legal wrangling -- and more than 100 days after the release of his report detailing Russia's attempts to interfere in the 2016 presidential election -- former special counsel Robert Mueller will take questions from Capitol Hill lawmakers throughout the day.

I am watching all of it and offering some key takeaways throughout the hearings. (Mueller will testify before the House Judiciary Committee this morning and the House Intelligence Committee this afternoon.) They're below.

1. Trump's tweets show how anxious he actually is...