popping

<style>
  .pop {
 font-size:2em;
 color: #000;
 text-align:center; /* looks weird often if not aligned in center */
 -webkit-animation: pop 1s ease-in-out infinite alternate;
 -moz-animation: pop 1s ease-in-out infinite alternate;
 animation: pop 1s ease-in-out infinite alternate;
}

@keyframes pop {
from { transform:scale(0.95) }
50% { transform:scale(1) }
to { transform:scale(0.95) }
}

@-webkit-keyframes pop {
from { -webkit-transform:scale(0.95) }
50% { -webkit-transform:scale(1) }
to { -webkit-transform:scale(0.95) }
}
</style>

<div class="pop">popping</div>