How do I get my text on a single line when I rotate in CSS

I'm rotating a Cell with

height: 500px;
width: 20px;
-webkit-transform:rotate(270deg);
-moz-transform:rotate(270deg);
-ms-transform:rotate(270deg);
-o-transform:rotate(270deg);
transform:rotate(270deg);

But when my string contain more than 1 word, it's going on multi-line (like the picture below)