<div class="smallit" onclick="javascript: $(this).toggleClass('largeit');">{mp4}video1{/mp4}</div>

.smallit {
     width:33%;
     float:left;
     padding: 0 45px 10px 0;
    -webkit-transition: width 1s ease-in-out;
    -moz-transition: width 1s ease-in-out;
    -o-transition: width 1s ease-in-out;
    transition: width 1s ease-in-out; 
 }
 
.largeit {
     width:100%;
     
    -webkit-transition: width 1s ease-in-out;
    -moz-transition: width 1s ease-in-out;
    -o-transition: width 1s ease-in-out;
    transition: width 1s ease-in-out; 
 }