<div class="container">
 <div class="search">
  <input type="text" placeholder="Search...">
  <button type="submit"><i class="fa fa-search"></i></button>
 </div>
</div>

* {
	box-sizing: border-box;
	outline: 0;
	font-family: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
}
body {
	background: #E55D87;
	background: -webkit-linear-gradient(to left, #5FC3E4, #E55D87);
	background: -moz-linear-gradient(to left, #5FC3E4, #E55D87);
	background: linear-gradient(to left, #5FC3E4, #E55D87);
}
.container {
	width: 400px;
	height: 50px;
	position: absolute;
	top: calc(50% - 25px);
	left: calc(50% - 200px);
}
.container .search {
	position: relative;
	height: 100%;
}
.container .search input {
	width: 50px;
	height: 50px;
	position: absolute;
	right: calc(50% - 25px);
	top: 0;
	padding: 0 25px;
	border: 0;
	border-radius: 25px;
	color: #4e4e4e;
	font-size: 18px;
	font-weight: 300;
	box-shadow: 0 5px 12px 0 rgba(0, 0, 0, 0.1),
		0 1px 28px 0 rgba(0, 0, 0, 0.2),
		0 0 40px 0 rgba(0, 0, 0, 0.1);
	transition: all 0.6s cubic-bezier(0, 2, 1, -1);
}
.container .search button {
	width: 50px;
	height: 50px;
	position: absolute;
	right: calc(50% - 25px);
	top: 0;
	margin: auto;
	background: #2d2926;
	color: #fff;
	font-size: 15px;
	border: 0;
	border-radius: 50%;
	box-shadow: 0 6px 28px 0 rgba(0, 0, 0, 0.0), 0 5px 55px 0 rgba(0, 0, 0, 0.0);
	cursor: pointer;
	transition:all 0.6s cubic-bezier(0, 2, 1, -1);
}

.container .search input:focus,
.container .search input:active,
.container .search:hover input {
	width: 400px;
	right:0;
}
.container .search input:focus + button,
.container .search input:active + button,
.container .search:hover button {
	right: 0;
	box-shadow: 0 6px 28px 0 rgba(0, 0, 0, 0.3), 0 5px 55px 0 rgba(0, 0, 0, 0.2);
}