SOURCE

<div class="box">

    <div class="item item1">item1</div>
    <div class="item item2">item2</div>
    <div class="item item3">item3</div>
    <div class="item">item4</div>
    <div class="item">item5</div>
    <div class="item">item6</div>
    <div class="item">item7</div>
    <div class="item">item8</div>
    <div class="item">item9</div>
    <div class="item">item10</div>
</div>

.box{
  display:flex;
  width:300px;
  height:200px;
  border:1px solid black;
  align-content:baseline;
  flex-wrap:wrap;
}
.item{ 
  width:60px;
  height:20px;
  border:1px solid black; 
  font-size:12px;
}
.item1{
  height:20px;
  font-size:8px;
  
}
.item2{
  height:30px;
  font-size:16px;
}
.item3{
  height:40px; font-size:18px;
}