According to Michael Cohen, one of his frequent jobs was renegotiating bills on Trump's behalf.

"A law firm would send an invoice. He didn't believe that the invoice was fair, reasonable or justified, so he would give me the task of renegotiating a specific bill," Cohen said.

Cohen recounted his work repaying approximately 50 vendors related to Trump University at a discounted rate. All but two of the fifty vendors agreed to the discounted rate.

"They just went away," Cohen said of the two vendors.

"Did you pay then?" prosecutor Susan Hoffinger asked.

"No, ma'am," Cohen responded.

Cohen said Trump told him the outcome of the negotiation was "fantastic" and "great."

"How did that make you feel?" Hoffinger asked.

"Like I was on top of the world," Cohen responded.

Cohen told jurors that he began working for Trump after helping Trump with a series of legal favors.

"We ended up overtaking the board and resolving the issue which was to Mr. Trump's satisfaction," Cohen said about the first favor related to a board at a Trump property. "He liked the way that occurred and then continued to ask me if I would assist in other legal issues or matters he had."

"Did he pay you for that work?" prosecutor Susan Hoffinger said.

"No, ma'am," Cohen said

According to Cohen, Trump offered him a job after he presented Trump a $100,000 bill for legal costs related to the earlier favors.

"Would you want to come work for me?" Cohen recounted Trump saying. "I was honored, I was taken by surprise, and I agreed"

When asked about the $100,000 legal bill, Cohen said Trump "asked if I would like to get fired on the first day." The bill was never paid, according to Cohen, who immediately left his law firm to work for the Trump Organization as Trump's special counsel and a senior vice president.

When asked about the kind of work Cohen did for Trump, Cohen responded, "It was whatever concerned him -- whatever he wanted."

Cohen said he reported "just to Mr. Trump."

Michael Cohen briefly introduced himself to the jury, telling them how his father immigrated to California after surviving the Holocaust.

"Four children later, here I am," Cohen said about his parents.

Cohen told the jury that he went to law school at the urging of his family, though he did not want to practice law.

"I wanted to go to Wall Street," Cohen said.

He briefly explained how he acquired wealth with real estate investments and taxi medallions.

"I ended up going into business with a friend of mine who had grown up with me and we started purchasing buildings," Cohen said.

Cohen stood up in the witness box so he could identify Trump in the courtroom.

"He is wearing a blue and white tie," Cohen said while looking toward Trump.

"The people call Michael Cohen," prosecutor Susan Hoffinger said.

Michael Cohen entered the courtroom and took his seat in the witness box.

Donald Trump stared straight forward as Cohen walked into the courtroom. He did not appear to look toward Cohen.

Defense attorney Todd Blanche continued to work to paint a picture of Michael Cohen as a proven liar who pleaded guilty to crimes associated with those lies and leveraged his cooperation as part of those plea deals to secure a shorter prison sentence.

"When you plead guilty to a crime, one of the things you get -- one of the benefits you get -- is a little time off your sentence ... correct?" Blanche asked.

Blanche then said that in the case of Cohen's guilty plea to charges that included those related to the Stormy Daniels payment, "You got that credit even though you lied."

Cohen, for his part, has claimed some responsibility for the hush money charges Donald Trump now faces -- but he has suggested that he himself should not have been charged, and that the system that charged him was "corrupt."

"Do you have any doubt in your mind that the outcome of this trial affects you personally?" Blanche asked Cohen.

"Yes," Cohen replied.