President Obama's executive order is set to move forward in the coming months and could potentially affect 4 to 5 million undocumented people in the US.

The largest number are right here in California.

But at the federal level, challenges are already brewing and Republican leadership in Congress has pledged to fight the president's plan.

For more, we're joined by Marielena Hincapié, executive director of the National Immigration Law Center, a legal advocacy group in Washington D.C., Los Angeles and Oakland.