<div class="container">
  <p></p>
  <div class="wrap">
    <div class="element element-1">
      50% 50%
    </div>
  </div>
  <div class="wrap">
    <div class="element element-2">
      top left      
    </div>
  </div>
  <div class="wrap">
    <div class="element element-3">
      100% 100%       
    </div>
  </div>
  <div class="wrap">
    <div class="element element-4">
      100px 50px       
    </div>
  </div>
</div>
body {
  background-color: #F5F5F5;
  color: #555;
  font-size: 1.1em;
  font-family: 'Helvetica Neue', Helvetica, Arial, sans-serif;
}

hr {
  margin: 50px 0;
}

.container {
  margin: 40px auto;
  max-width: 800px;
}

.wrap {
  width: 150px;
  height: 150px;
  border: 2px solid grey;
  display: inline-block;
  margin: 100px;
}

.element {
  width: 150px;
  height: 150px;
  position: relative;
  color: white;
  text-align: center;
  line-height: 150px;
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
}

.element-1 {
  background-color: #009966;
}

.element-2 {
  background-color: purple;
  -webkit-transform-origin: top left;
  -ms-transform-origin: top left;
  transform-origin: top left;
}

.element-3 {
  background-color: #0099ee;
  -webkit-transform-origin: 100% 100%;
  -ms-transform-origin: 100% 100%;
  transform-origin: 100% 100%;
}

.element-4 {
  background-color: orange;
  -webkit-transform-origin: 100px 50px;
  -ms-transform-origin: 100px 50px;
  transform-origin: 100px 50px;
}