ul.thumbnailmatrix {
    display: flex;
    flex-flow: row wrap;
    justify-content: flex-start;
    padding-left: 0;
}

ul.thumbnailmatrix li {
    margin: 0 1.5em 3em .5em;
    padding: 0;
}

ul.thumbnailmatrix figure {
    margin: 0;
    padding: 0;
    display: flex;
    flex-direction: column;
}


ul.thumbnailmatrix figcaption {
    width: 140px;  /* Same width as the thumbnail images */
}