<style>
.parent {
    font-size: 20px;
    }
.child {
    font-size: 2em;
    }
.para {
    font-size: 12px;
    }
</style>
<div class="parent">
    <p> This is a parent paragraph.</p>
    <div class="child">
        <p> This is a child paragraph.</p>
    </div>
    <p class="para"> The size of this paragraph is not affected by parent size.</p>
</div>