<link href="//netdna.bootstrapcdn.com/font-awesome/4.0.3/css/font-awesome.min.css" rel="stylesheet">
<div class="inner">
  <form id="searchform">
    <input type="text" id="text">
    <input type="submit" id="submit">
  </form>
  <a href="#" class="search-btn"><i class="fa fa-search"></i></a>
</div>
* {
  box-sizing: border-box;
}

.inner {
  position: relative;
  height: 44px;
  margin: 0 auto;
  width: 44px;
}

.search-btn {
  background: #F27398;
  border-radius: 50%;
  display: inline-block;
  height: 44px;
  line-height: 44px;
  margin: 0 auto;
  position: absolute;
  top: 0;
  text-align: center;
  width: 44px;
}

.search-btn i {
  color: #fff;
  margin: 0;
}

#searchform {
  height: 44px;
  margin: 0 auto;
  position: absolute;
  top: 0;
  width: 44px;
}

input[type="text"] {
  background: #ccc;
  border: none;
  border-radius: 22px;
  color: #333;
  cursor: pointer;
  height: 44px;
  opacity: 0;
  outline: none;
  padding: 5px;
  position: absolute;
  top: 0;
  right: 0;
  transition: all 0.7s;
  width: 44px;
  z-index: 5;
}

input[type="submit"] {
  display: none;
}

input[type="text"]:focus {
  cursor: text;
  opacity: 1;
  width: 300px;
}

External CSS

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External JavaScript

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