How do you minimize the keyboard when texting

I'm sorry if this has been asked already.

I have a question. When you are texting someone and you want to shrink the keyboard down, how do you do it? The only way I can seem to do it is to back all the way out of the message, then re-enter. I can then read the texts. But as soon as I type a reply, the keyboard is back to full size, and I can't shrink it down again.

Thank you for any information that you can give.