<div class="accordion">
  
  <div class="in">
    <label>
      <input type="checkbox" name="option" >
       <h3>Текст 1</h3>
       <div class="out">
         Lorem ipsum dolor sit amet consectetur adipisicing elit. Fuga laborum ab expedita ex alias iusto, quas voluptas voluptatem. Exercitationem sint fugiat odit ipsa culpa aliquid numquam! Alias ipsum itaque porro.
      </div>
    </label>
  </div>
  
  <div class="in">
    <label>
      <input type="checkbox" name="option" >
       <h3>Текст 2</h3>
       <div class="out">
         Lorem ipsum dolor sit amet consectetur adipisicing elit. Fuga laborum ab expedita ex alias iusto, quas voluptas voluptatem. Exercitationem sint fugiat odit ipsa culpa aliquid numquam! Alias ipsum itaque porro.
      </div>
    </label>
  </div>
  
  <div class="in">
    <label>
      <input type="checkbox" name="option">
       <h3>Текст 3</h3>
       <div class="out">
         Lorem ipsum dolor sit amet consectetur adipisicing elit. Fuga laborum ab expedita ex alias iusto, quas voluptas voluptatem. Exercitationem sint fugiat odit ipsa culpa aliquid numquam! Alias ipsum itaque porro.
      </div>
    </label>
  </div>
  
</div>

*{
  user-select: none;
}

.accordion{
  width: 500px;
  margin: 40px  auto;
  font-family: sans-serif;
}

.in{
  width: 100%;
  overflow: hidden;
  border: 1px solid #ccc;
  border-radius: 6px;
  background: #fff;
  margin-top: 6px;
}

[type='checkbox']{
  display: none;
}

h3{
  display: inline-block;
  padding: 10px;
  margin: 0;
  width: 100%;
  font-weight: 500;
  font-size: 14px;
  width: 100%;
  text-transform: uppercase;
}

.out{
  height: 0;
  transform: scaleY(0);
  transition: 0.2s cubic-bezier(.2,.1,.8,1.4);
  padding: 0;
  margin: auto;
  opacity: 0;
  font-weight: 100;
  font-size: 14px;

}

.out img{
  display: block;
  width: 100%;
  margin: 16px 0;
}

input:checked ~ .out{
  transform: scaleY(1);
  height: auto;
  opacity: 1;
  padding: 30px;
}

input:checked ~ h3{
  background: #fafafa;
}