ds

<div class="wrap">
  <input type="checkbox" name="slide1" class="none" id="slide1" />
  <label for="slide1">показати</label>
  <p class="show">some text here</p>
</div>

gistfile1.txt

.none {
  display: none;
}

p {
  height: 0;
  overflow: hidden;
  transition: height 300ms ease;
}

#slide1:checked ~ .show {
  height: 100px;
}