How to create a basic tooltip using CSS3

One of the projects I'm working on requires basic menu items that are styled like tooltips. Below is a very simple example of how to achieve that style by creating a CSS triangle and using the :after selector.

We'll just call the element .tooltip

<div class="tooltip">item</div>

.tooltip {
    height: 50px;
    width: 50px;
    max-width: 50px;
    display: inline-block;
    padding: 5px;
    position: absolute;
    color: rgba(255, 255, 255, 0.9);
    line-height: 50px;
    text-align: center;
    background: #3C8BBD;
    box-shadow: 0 1px 4px rgba(0, 0, 0, 0.1);
}

.tooltip:after {
    content: "";
    border-width: 8px 6px 0 6px;
    border-style: solid;
    border-color: #3C8BBD rgba(0, 0, 0, 0);
    display: block;
    position: absolute;
    bottom: -8px;
    left: 50%;
    margin-left: -6px;
    z-index: 220;
    width: 0;
}