Don't Break

When you need text to stay inside its container, use this. A fantastic explanation of this is on CSS Tricks.

<style>
  .break {
  
    width: 100px;
  
    /* This is what happens when the W3C can't make up their minds. 
    These two lines mean the same thing. */
    overflow-wrap: break-word;
    word-wrap: break-word;
    
    -ms-word-break: break-all;
    word-break: break-all;
    word-break: break-word;
  
    /* Add hyphens */
    -webkit-hyphens: auto;
    -ms-hyphens: auto;
    -moz-hyphens: auto;
    hyphens: auto;
  
  }
</style>

<div class="break">
  areallylongunbrokenpiceoftextthathasnobusinessbeingonthewebinthefirstplace
</div>

See it in action.