.thumbnail-container {
  position: relative;
  display: inline-block;
}

.thumbnail {
  width: 150px;
  height: 150px;
  display: block;
  cursor: pointer;
}

.preview {
  position: absolute;
  top: ;
  left: -230px;
  width: 600px;
  height: 337px;
  opacity: 0;
  visibility: hidden;
  transition: opacity 4.0s ease;
  z-index: 10;
  border: 1px solid #ccc;
  background: #fff;
  box-shadow: 0 0 10px rgba(0,0,0,0.2);
}

.thumbnail-container:hover .preview {
  opacity: 1;
  visibility: visible;
}

.preview img {
  width: 100%;
  height: auto;
}