Sen. Bernie Sanders held his 2020 campaign kick off rally at Brooklyn College in New York City on Saturday.

The crowd, which the campaign said was roughly 13,000 strong, was young and diverse.

"Brothers and sisters, we are going to win this election ... because we are putting together the strongest grassroots campaign in the history of US politics," Sanders declared to the roaring audience.

Sanders also used his speech as an opportunity to reflect on his Brooklyn childhood, contrasting his humble beginnings to President Donald Trump's affluent roots in Queens.

BROOKLYN, NY — Sen. Bernie Sanders held his first big 2020 campaign rally in his childhood home of Brooklyn, New York, on Saturday, drawing in a massive, youthful, and diverse crowd.

It was a cold, snowy day at Brooklyn College, where the event took place, but that didn't stop thousands of Sanders supporters from turning out.

INSIDER was on the scene as the Vermont senator launched what he hopes will be the campaign that boots President Donald Trump out of the White House.

Here's how Sanders' 2020 kick off event unfolded.