Material Design: z-index

mui-zindex

body {
  background: #eee;
}

.card {
  background: #fff;
  border-radius: 2px;
  display: block;
  float: left;
  height: 50px;
  margin: 1rem;
  position: relative;
  width: 50px;
}

.mui-z1 {
  box-shadow: 0 0px 2px rgba(0,0,0,0.12), 0 2px 2px rgba(0,0,0,0.24);
  transition: all 0.2s ease-in-out;
}

.mui-z1:active {
  box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23);
}

.mui-z2 {
  box-shadow: 0 3px 6px rgba(0,0,0,0.16), 0 3px 6px rgba(0,0,0,0.23);
}

.mui-z3 {
  box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);
}

.mui-z4 {
  box-shadow: 0 14px 28px rgba(0,0,0,0.25), 0 10px 10px rgba(0,0,0,0.22);
}

.mui-z5 {
  box-shadow: 0 19px 38px rgba(0,0,0,0.30), 0 15px 12px rgba(0,0,0,0.22);
}