#gallery {
    line-height:0;
    -webkit-column-count:5; /* split it into 5 columns */
    -webkit-column-gap:5px; /* give it a 5px gap between columns */
    -moz-column-count:5;
    -moz-column-gap:5px;
    column-count:5;
    column-gap:5px;
 }

 #gallery img {
    width: 100% !important;
    height: auto !important;
    margin-bottom:5px; /* to match column gap */
   filter: grayscale(50%);
    transition: filter 0.5s;
 }

 #gallery img:hover {
    filter:none;
 }

 @media (max-width: 1200px) {
    #gallery {
     -moz-column-count:    4;
     -webkit-column-count: 4;
     column-count:         4;
    }
 }

 @media (max-width: 1000px) {
    #gallery {
     -moz-column-count:    3;
     -webkit-column-count: 3;
     column-count:         3;
    }
 }

 @media (max-width: 800px) {
    #gallery {
     -moz-column-count:    2;
     -webkit-column-count: 2;
     column-count:         2;
    }
 }

 @media (max-width: 400px) {
    #gallery {
     -moz-column-count:    1;
     -webkit-column-count: 1;
     column-count:         1;
    }
 }