要在将鼠标悬停在元素上时显示溢出的内容，可以尝试运行以下代码：
<!DOCTYPE html>
<html>
<head>
<style>
div.demo {
white-space: nowrap;
width: 180px;
overflow: hidden;
border: 2px solid blue;
}
div.demo:hover {
text-overflow: inherit;
overflow: visible;
}
</style>
</head>
<body>
<p>Hover to see the complete text below:</p>
<br>
<div class = "demo" style = "text-overflow:clip;">Demo Text that will hide in this box.</div>
</body>
</html>