<img src="http://lorempixel.com/output/city-q-g-200-200-8.jpg" alt="" />
body{
  background-color: rgb(230,230,230);
}
img{
  transition: width,height;
  transition-duration: 1s;
  width: 200px;
  height: 200px;
}
img:hover{
  width: 230px;
  height: 230px;
}

External CSS

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External JavaScript

This Pen doesn't use any external JavaScript resources.