Edit in JSFiddle


              
body {
  background-color: #cdcdcd;
}

.stackpic {
  width: 40px;
  height: 40px;
  border: 5px solid #fff;
  border-radius: 50%;
  float: left;
}

.stackpic:not(:first-child) {
  margin-left: -20px;
}
<div class="container">
  <img class="stackpic" src="https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png">
  <img class="stackpic" src="https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png">
  <img class="stackpic" src="https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png">
  <img class="stackpic" src="https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png">
  <img class="stackpic" src="https://cdn.pixabay.com/photo/2016/08/08/09/17/avatar-1577909_960_720.png">
</div>