#box {
   -webkit-animation: animacao 1s ease alternate both;
}

@-webkit-keyframes animacao {
   from { 
  transform: scale(0);
  -webkit-transform: scale(0);
  -moz-transform: scale(0);
  -o-transform: scale(0);
  -ms-transform: scale(0);  }
   to { 
transform: scale(1);
-webkit-transform: scale(1);
-moz-transform: scale(1);
-o-transform: scale(1);
-ms-transform: scale(1);  }
}