Creating fields for profiles, but want multi line entry not single line

Whenever you add a field to your profiles, it's always a single line entry field. I want an entry field that is like a box or multiple line entry. So people can type something like

blah
blah
blah

instead of having to type blah blah blah in one single line.

How can I change this? I would think it would be fairly easy, but I don't know how to do it. Can somebody please help me?