Edit in JSFiddle

<div class="wrapper">
  <div>1</div>
  <div>2</div>
  <div>3</div>
  <div>4</div>
  <div>5</div>
  <div>6</div>
  <div>7</div>
  <div>8</div>
  <div>9</div>
</div>
* { box-sizing: border-box; }

body {
  margin: 40px;
  background-color: #fff;
  color: #444;
  font: 2em Sansita, sans-serif;
}

.wrapper {
  display: flex;
  flex-wrap: wrap;
}

.wrapper > * {
  flex: 1 1 200px; // Play around with this
  border: 5px solid rgb(214,129,137);
  border-radius: 5px;
  margin: 10px;
  padding: 10px 20px;
  background-color: #29d19c;
  color: #fff;
}