Height Complex
<div class="flexbox-parent">
    <div class="flexbox-item header">
        Header
    </div>
    
    <div class="flexbox-item fill-area content flexbox-item-grow">
        <div class="fill-area-content flexbox-item-grow">
            Content 
            <br /><br />
            Emulates height 100% with a horizontal flexbox with stretch
            <br /><br />      
            This box with a border should fill the blue area except for the padding (just to show the middle flexbox item).
        </div>
    </div>
    
    <div class="flexbox-item footer">
        Footer
    </div>
</div>
/**
// height? 100 > 1000 > 10000
*/
*, *:before, *:after {
	-moz-box-sizing: border-box;
	-webkit-box-sizing: border-box;
	box-sizing: border-box;
}
html, body {
    width: 100%;
    height: 100%;    
    margin: 0;
    padding: 0;
}
body {
    background: #444444;    
    color: #cccccc;
    font-size: 14px;
    font-family: Frutiger, "Frutiger Linotype", Univers, Calibri, "Gill Sans", "Gill Sans MT", "Myriad Pro", Myriad, "DejaVu Sans Condensed", "Liberation Sans", "Nimbus Sans L", Tahoma, Geneva, "Helvetica Neue", Helvetica, Arial, sans-serif;
}
.flexbox-parent {
    width: 100%;
    height: 100%;
    display: flex;
    flex-direction: column;    
    justify-content: flex-start;
    align-items: stretch;
    align-content: stretch;            
    background: rgba(255, 255, 255, .1);
}
.flexbox-item {
    padding: 8px;
}
.flexbox-item-grow {
    flex: 1; /* flex: 1 1 auto; */
}
.flexbox-item.header {
    background: rgba(255, 0, 0, .1);
}
.flexbox-item.footer {
    background: rgba(0, 255, 0, .1);
}
.flexbox-item.content {
    background: rgba(0, 0, 255, .1);
}
.fill-area {
    display: flex;
    flex-direction: row;    
    justify-content: flex-start;
    align-items: stretch;
    align-content: stretch;    
}
.fill-area-content {
    background: rgba(0, 0, 0, .3);
    border: 1px solid #000000;
    overflow: auto; 
}
/*js*/