Minimum height by css in html

Minimum height by css in html

I'm creating web site layout.

This is label3 css :
background-color:#c4efd5;
min-height:368px;
height:100%;
I want to set minimum height of lable3 to 368px even it does not contain
any data. And when I insert image height = 450px, label3 will be re-size
height to 450px.
I'm using min-height to do that, but it did not display as I expected.
Any answer will be appreciate. Thanks you.