如何使用CSS在DIV中垂直对齐图像和文本?

I have an image and some text inside a div and I'd like to put the image and the text in the vertical center of the div using CSS. The problem is that I don't know how many lines of text I will have but the text and the image must be ALWAYS in the middle. For example, when there's only one line of text the div should look like this:I have an image and some text inside a div and