A Pen by Stan Williams.

index.html

<h1>Photo Gallery in CSS3</h1>
<!-- modified by Stan williams
 http://codepen.io/Stanssongs
http://stans-songs.com  So far I have I made sizing be responsive, and added text  styles 
<h2>H2 text 2.5em</h2>
<h3>H3 text  2em</h3>
<p> text </p> -->
<div id="gal">
  <ul>
    <li>
      <img src="http://placekitten.com/300/300" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300" class="img" />
    </li>
    <li>
      <img src="http://placekitten.com/300/300?image=3" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300?image=3" class="img" />
    </li>
    <li>
    <img src="http://placekitten.com/300/300?image=1" class="small" width="100" height="100" alt="" /><img src="http://placekitten.com/300/300?image=1" class="img" />
    </li>
    <li>
   <img src="http://placekitten.com/300/300?image=2" class="small"  width="100" height="100" alt="" /><img src="http://placekitten.com/300/300?image=2" class="img" />
    </li> 
    <li><li>
   <img src="http://placekitten.com/300/300?image=5" class="small"  width="100" height="100" alt="" /><img src="http://placekitten.com/300/300?image=5" class="img" />
    </li> 
    <li>
      <img src="http://placekitten.com/300/300?image=3" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300?image=3" class="img" />
    </li> 
    <li>
      <img src="http://placekitten.com/300/300?image=2" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300?image=2" class="img" />
    </li>
    <li>
      <img src="http://placekitten.com/300/300?image=4" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300?image=4" class="img" />
    </li>
    <li>
      <img src="http://placekitten.com/300/300" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300" class="img" />
    </li>
    <li>
    <img src="http://placekitten.com/300/300?image=2" class="small" width="100" height="100" alt="" /><img src="http://placekitten.com/300/300?image=2" class="img" />
    </li>
    <li>
   <img src="http://placekitten.com/300/300" class="small"  width="100" height="100" alt="" /><img src="http://placekitten.com/300/300" class="img" />
    </li> 
   
    <li>
      <img src="http://placekitten.com/300/300?image=4" class="small" width="100" height="100" /><img src="http://placekitten.com/300/300?image=4" class="img" />
    </li> 
   
  </ul>
</div>

script.js

//    2014-03-23
 //forked from original author sniperwolf http://codepen.io/sniperwolf/pen/LDGdq

// Copyright (c) 2014 Stan Williams

// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:

// The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

Simple-Gallery-in-CSS3.markdown

Simple Gallery in CSS3

A Pen by Stan Williams on CodePen.

License.

style.css

body {
    color: #FFFFFF;
    background: #10a350;
    text-align: center;
    font-size: 1em;
}

h1 {
    color: #FFFFFF;
    font-size: 3em;
    text-shadow: #333333 2px 2px 4px;
}
h2 {
    color: #FFFFFF;
    font-size: 1em;
    text-shadow: #333333 2px 2px 4px;
}
h3 {
    color: #FFFFFF;
    font-size: 2em;
    text-shadow: #333333 2px 2px 4px;
}
 

#gal {
    background: #333333;
    border: 5px solid #111111;
    border-radius: 20px;
    margin-left: auto;
    margin-right: auto;
    overflow: visible;
    height: 70%;
    width: 70%;
    filter: progid:DXImageTransform.Microsoft.Shadow(color='#333333', Direction=135, Strength=10);
    box-shadow: #333333 15px 25px 200px;
}

#gal ul {
   margin-left: -15px;
}

#gal ul li {
    display: inline-table;
    list-style: none;
    padding: 15px;
}

#gal ul li .img {
    border: 1px solid #000000;
    box-shadow: #333333 5px 5px 10px;
    margin-top: -50px;
    margin-left: -50px;
    position: absolute;
    opacity: 0;
    visibility: hidden; filter:progid:DXImageTransform.Microsoft.Shadow(color='#333333', Direction=135, Strength=5);
  
    -webkit-transition: all 0.4s ease-in-out;
    -moz-transition: all 0.4s ease-in-out;
    -o-transition: all 0.4s ease-in-out;
    transition: all 0.4s ease-in-out;
}

#gal ul li:hover .img {
    float: right;
    height: 300px;
    opacity: 1;
    width: 300px;
    visibility: visible;
}

Preview it full size here : http://codepen.io/Stanssongs/full/AKyeF
Demo Preview fork it and or and edit it live here http://codepen.io/Stanssongs/pen/AKyeF