.bubble {
    margin: 50px;
    padding: 20px;
    position: relative;
    border-radius: 8px 8px 8px 8px;
    width: 200px;
    box-shadow: 0 0 10px gray;
}

.bubble:after {
    content: "";
    position: absolute;
   top: 100%;
   left: 20px;
   border-top: 20px solid blue;
   border-top-color: inherit;
   border-left: 20px solid transparent;
   border-right: 20px solid transparent;
    box-shadow: 0 0 10px gray;

}