CSS On hover show another element

I want to use CSS to show div id='b' when I hover over div id='a', but I cannot figure out how to do it because the div 'a' is inside another div that div 'b' is not in.

<div id='content'>
     <div id='a'>
         Hover me
     </div>
</div>
<div id='b'>
    Show me
</div>

we just can show same label div on hovering like this

<style>
#b {
    display: none;
}

#content:hover~#b{
    display: block;
}

</style>

It is indeed possible with the following code

 <div href="#" id='a'>
     Hover me
 </div>

<div id='b'>
    Show me
</div>

and css

#a {
  display: block;
}

#a:hover + #b {
  display:block;
}

#b {
  display:none;
  }

Now by hovering on element #a shows element #b.

You can use axe selectors for this.

There are two approaches:

1. Immediate Parent axe Selector (<)

#a:hover < #content + #b

This axe style rule will select #b, which is the immediate sibling of #content, which is the immediate parent of #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;
}

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);
}

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;
}

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;
}

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);
}

#a:hover < #content + #b {
display: inline-block;
}

<div id="content">
<div id="a">Hover me</div>
</div>

<div id="b">Show me</div>

<script src="https://rouninmedia.github.io/axe/axe.js"></script>

---

2. Remote Element axe Selector (\)

#a:hover \ #b

This axe style rule will select #b, which is present in the same document as #a which has a :hover state.

div {
display: inline-block;
margin: 30px;
font-weight: bold;
}

#content {
width: 160px;
height: 160px;
background-color: rgb(255, 0, 0);
}

#a, #b {
width: 100px;
height: 100px;
line-height: 100px;
text-align: center;
}

#a {
color: rgb(255, 0, 0);
background-color: rgb(255, 255, 0);
cursor: pointer;
}

#b {
display: none;
color: rgb(255, 255, 255);
background-color: rgb(0, 0, 255);
}

#a:hover \ #b {
display: inline-block;
}

<div id="content">
<div id="a">Hover me</div>
</div>

<div id="b">Show me</div>

<script src="https://rouninmedia.github.io/axe/axe.js"></script>