Change post titles to lowercase

Hello!

I would like to know how to change ALL my post titles to lower case?

All my post titles are in upper case by default and it doesn’t look so good to me. I just wanna capitalize the first letter of each word of my post titles, but I can’t!

This is my first post :

http://www.hacklearner.com/hello-everybody/

and the post title is : HELLO EVERYBODY OUT THERE and not ” Hello Everybody Out There”

I’m using a child theme 🙂

How can I fix that?

Thanks.