Demo

HTML

<div class="more"></div>

CSS

body, html{
    width:100%;
    height:100%;
    margin:0;
    padding:0;
}
.more{
    width:50px;
    height:50px;
    background:#999;
}

JavaScript

$('.more').click(function(){
    var isFullscreen = false;
    var d = {};
    var speed = 900; 
    if(!isFullscreen){ // MAXIMIZATION
        d.width = $(window).width();;
        d.height = $(window).height();; 
        isFullscreen = true;
    }
    else{ // MINIMIZATION            
        d.width = "50px";
        d.height =  "50px";            
        isFullscreen = false;
    }

    $(this).animate(d,speed)
    })