Best Practice for Form Layout – UI

I'm building out a form at the top of page, where we are collecting 3 pieces of information. Would it be best to display this one line at a time or show all at once?

Scenario 1: - The first form field shows up. Upon being filled out, a second field appears underneath it. Once that is filled out, the third and final field appears below that. So the form expands as it's being completed.

Scenario 2: - All 3 fields appear at once.