How to vertically align 2 different sizes of text?

I know to vertically align text to the middle of a block, you set the line-height to the same height of the block.

However, if I have a sentence with a word in the middle, that is 2em. If the entire sentence has a line-height the same as the containing block, then the larger text is vertically aligned but the smaller text is on the same baseline as the larger text.

How can I set it so both sizes of text are vertically aligned, so the larger text will be on a baseline lower than the smaller text?

Try vertical-align:middle; on inline containers?

EDIT : it works but all your text must be in an inline container, like this :

    <div style="height:100px; line-height:100px; background:#EEE;">
        <span style="vertical-align:middle;">test</span>
        <span style="font-size:2em; vertical-align:middle;">test</span>
    </div>

The functionality you are seeing is correct because the default for "vertical-align" is baseline. It appears that you want vertical-align:top. There are other options. See here at W3Schools.

Edit W3Schools has not cleaned up their act and still, appear, to be a shoddy (at best) source of information. I now use sitepoint. Scroll to the bottom of the sitepoint front page to access their reference sections.

the two set of text must have the same fixed line-height and the vertical-align set

 span{
     vertical-align: bottom;
     line-height: 50px;
}

Easy way - use flex:

<div>
        abcde
        &nbsp;&nbsp;
        <span>efghai</span>
</div>

<style>
    div {
        padding: 20px;
        background-color: orange;
        display: flex;
        align-items: center; }

    span {
        font-size: 1.5em; }
</style>

You technically can't, however, if you have fixed text sizes you could use positioning (relative) to move the larger text down and set the line-height to the smaller text (I'm presuming this larger text is marked up as such so you can use that as a CSS selector)

You can use percentage sizes to reapply the parent's line-height

.big {
  font-size: 200%;
  line-height: 25%;
  display: inline-block;
  vertical-align: middle;
}

Utque aegrum corpus <span class="big">etiam</span> levibus solet offensis 

An option is to use a table there the different sized texts are in their own cells and use align:middle on each cell.

Its not pretty and does not work for all occasions, but it is simple and works with any text size.

This works

header > span {
    margin: 0px 12px 0px 12px;
    vertical-align:middle;
}
.responsive-title{
    font-size: 12vmin;
    line-height: 1em;
}
.responsive-subtitle{
    font-size: 6vmin;
    line-height: 2em;
}

<header>
  <span class="responsive-title">Foo</span>
  <span class="responsive-subtitle">Bar</span>
</header>