SOURCE

<div class="outer outer4">
        <div class="inner inner4">
            <p>first line</p>
            <p>second line</p>
        </div>
    </div>

.outer4 {
    position: relative;
}

.inner4 {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
    margin: auto;
    width: 100px;
    height: 80px;
}