<div class="grid grid-1">
  <div class="item">
    <div class="item-content">1</div>
  </div>
  <div class="item">
    <div class="item-content">2</div>
  </div>
  <div class="item">
    <div class="item-content">3</div>
  </div>
  <div class="item">
    <div class="item-content">4</div>
  </div>
  <div class="item">
    <div class="item-content">5</div>
  </div>
  <div class="item">
    <div class="item-content">6</div>
  </div>
  <div class="item">
    <div class="item-content">7</div>
  </div>
  <div class="item">
    <div class="item-content">8</div>
  </div>
  <div class="item">
    <div class="item-content">9</div>
  </div>
  <div class="item">
    <div class="item-content">10</div>
  </div>
  <div class="item">
    <div class="item-content">11</div>
  </div>
  <div class="item">
    <div class="item-content">12</div>
  </div>
  <div class="item">
    <div class="item-content">13</div>
  </div>
  <div class="item">
    <div class="item-content">14</div>
  </div>
  <div class="item">
    <div class="item-content">15</div>
  </div>
  <div class="item">
    <div class="item-content">16</div>
  </div>
  <div class="item">
    <div class="item-content">17</div>
  </div>
  <div class="item">
    <div class="item-content">18</div>
  </div>
  <div class="item">
    <div class="item-content">19</div>
  </div>
  <div class="item">
    <div class="item-content">20</div>
  </div>
</div>

<div class="grid grid-2">
  <div class="item">
    <div class="item-content">1</div>
  </div>
  <div class="item">
    <div class="item-content">2</div>
  </div>
  <div class="item">
    <div class="item-content">3</div>
  </div>
  <div class="item">
    <div class="item-content">4</div>
  </div>
  <div class="item">
    <div class="item-content">5</div>
  </div>
  <div class="item">
    <div class="item-content">6</div>
  </div>
  <div class="item">
    <div class="item-content">7</div>
  </div>
  <div class="item">
    <div class="item-content">8</div>
  </div>
  <div class="item">
    <div class="item-content">9</div>
  </div>
  <div class="item">
    <div class="item-content">10</div>
  </div>
  <div class="item">
    <div class="item-content">11</div>
  </div>
  <div class="item">
    <div class="item-content">12</div>
  </div>
  <div class="item">
    <div class="item-content">13</div>
  </div>
  <div class="item">
    <div class="item-content">14</div>
  </div>
  <div class="item">
    <div class="item-content">15</div>
  </div>
  <div class="item">
    <div class="item-content">16</div>
  </div>
  <div class="item">
    <div class="item-content">17</div>
  </div>
  <div class="item">
    <div class="item-content">18</div>
  </div>
  <div class="item">
    <div class="item-content">19</div>
  </div>
  <div class="item">
    <div class="item-content">20</div>
  </div>
</div>

body {
  display: flex;
  justify-content: space-evenly;
  margin: 20px 0;
}
.grid {
  position: relative;
  width: 48%;
  background: #ccc;
  border: 5px solid transparent;
}
.item {
  position: absolute;
  width: 100px;
  height: 100px;
  line-height: 100px;
  margin: 5px;
  z-index: 1;
}
.item.muuri-item-hidden {
  z-index: 0;
}
.item.muuri-item-releasing {
  z-index: 2;
}
.item.muuri-item-dragging {
  z-index: 3;
}
.item-content {
  position: relative;
  width: 100%;
  height: 100%;
  text-align: center;
  background: red;
  font-size: 30px;
  color: white;
  cursor: pointer;
}
.grid-2 .item-content {
  background: green;
}
.item.muuri-item-dragging .item-content,
.item.muuri-item-releasing .item-content {
  background: blue;
}

var grid1 = new Muuri('.grid-1', {
  dragEnabled: true,
  dragContainer: document.body,
  dragSort: function () {
    return [grid1, grid2]
  }
});

var grid2 = new Muuri('.grid-2', {
  dragEnabled: true,
  dragContainer: document.body,
  dragSort: function () {
    return [grid1, grid2]
  }
});