Why is these flex items not wrapping? - html

Question

I have a flex item that is also a flex container .sub-con, problem is the flex item of .sub-con is refusing to wrap, even after adding : flex-flow: row wrap.
Can anyone fix this for me, or point out what I'm doing wrong.
.container {
display: flex;
justify-content: center;
align-items: center;
flex-flow: row wrap;
height: 100vh;
}
.sub-con {
margin-right: 50px;
margin-left: 50px;
height: 500px;
background-color: #fff;
display: flex;
justify-content: center;
flex-flow: row wrap;
}
.col-one {
height: 100px;
border: 1px solid lightgreen;
flex-grow: 2;
}
.col-two {
height: 100px;
border: 1px solid red;
flex-grow: 1;
}
<div class="container">
<div class="sub-con">
<div class="col-one"></div>
<div class="col-two"></div>
</div>
</div>

Answer 1

Your flex items in the nested container are sized with percentages.
.col-one{
width: 40%;
height: 100px;
border: 1px solid lightgreen;
}
.col-two{
width: 40%;
height: 100px;
border: 1px solid red;
}
Because percentage lengths are based on the length of the parent they have no reason to wrap. They will always be 40% of the parent, even if the parent has a width of 1%.
If you use other units for length, such as px or em, they will wrap.
jsFiddle demo
.container {
display: flex;
justify-content: center;
align-items: center;
flex-flow: row wrap;
height: 100vh;
}
.sub-con {
flex: 1; /* for demo only */
align-content: flex-start; /* for demo only */
margin-right: 50px;
margin-left: 50px;
height: 500px;
background-color: #fff;
display: flex;
justify-content: center;
flex-flow: row wrap;
}
.col-one {
width: 200px;
height: 100px;
border: 1px solid lightgreen;
}
.col-two {
width: 200px;
height: 100px;
border: 1px solid red;
}
<div class="container">
<div class="sub-con">
<div class="col-one"></div>
<div class="col-two"></div>
</div>
</div>