<!DOCTYPE html>
<html lang="en-US">
<head>
<style>
body{
font-size:50px;
}
p{
font-size:1rem;
}
</style>
</head>
<body>
<p>font-size of the paragraphs are 1rem (1 times of html's font-size), i.e. the font-size of <html> tag (16px - default) not <body> tag (50px).<p> </body>
</html>