.fluidMedia {
    position: relative;
    padding-bottom: 100%; /* proportion value to aspect ratio 16:9 (9 / 16 = 0.5625 or 56.25%) */
    padding-top: 10px;
    height: 0;
    overflow: hidden;
}

    .fluidMedia iframe {
        position: absolute;
        top: 0;
        left: 0;
        width: 100%;
        height: 100%;
    }