#grid-container {
  width: 90%;
  margin: auto;
  overflow: hidden;
}

.grid-item {
  opacity: 0;
  float: left;
  box-sizing: border-box;
}

.grid-item img {
  width: 100%;
  height: 100%;
}

.grid-item.loaded {
  opacity: 1;
  transition: opacity .5s;
}