Create a Masonry grid with flexbox (or other CSS)

Question

I would like to achieve a grid effect in CSS with elements that all have the same width in size but not in height. I would like the element underneath to be always at 50px of the bottom one, whatever is next.

I tried with floats, but that bug. So I tried with Flex, but it still does not do what I want.

.container
  display: flex
  flex-wrap wrap
  align-content flex-start
  align-items flex-start

What I would like:

What I have:

Answer 1

Try the new CSS Grid Layout:

grid-container {
  display: grid;                                                /* 1 */
  grid-auto-rows: 50px;                                         /* 2 */
  grid-gap: 10px;                                               /* 3 */
  grid-template-columns: repeat(auto-fill, minmax(30%, 1fr));   /* 4 */
}

[short] {
  grid-row: span 1;                                             /* 5 */
  background-color: green;
}

[tall] {
  grid-row: span 2;
  background-color: crimson;
}

[taller] {
  grid-row: span 3;
  background-color: blue;
}

[tallest] {
  grid-row: span 4;
  background-color: gray;
}

<grid-container>
  <grid-item short></grid-item>
  <grid-item short></grid-item>
  <grid-item tall></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
  <grid-item taller></grid-item>
  <grid-item short></grid-item>
  <grid-item tallest></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
  <grid-item tallest></grid-item>
  <grid-item tall></grid-item>
  <grid-item taller></grid-item>
  <grid-item short></grid-item>
  <grid-item short></grid-item>
  <grid-item short></grid-item>
  <grid-item short></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
  <grid-item taller></grid-item>
  <grid-item short></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
  <grid-item short></grid-item>
  <grid-item tallest></grid-item>
  <grid-item taller></grid-item>
  <grid-item short></grid-item>
  <grid-item tallest></grid-item>
  <grid-item tall></grid-item>
  <grid-item short></grid-item>
</grid-container>