<div class="my-5">

  <section class="grey lighten-2 py-5">

    <div class="flex-center">

​

      <!--First row-->

      <div class="row">

​

        <!--First column-->

        <div class="col-md-3 flex-center">

          <img src="https://mdbootstrap.com/img/Photos/Template/34.png" class="img-fluid wow fadeIn" data-wow-delay=".2s">

        </div>

        <!--/First column-->

​

        <!--Second column-->

        <div class="col-md-3 flex-center">

          <img src="https://mdbootstrap.com/img/Photos/Template/35.png" class="img-fluid wow fadeIn" data-wow-delay=".4s">

        </div>

        <!--/Second column-->

​

        <!--Third column-->

        <div class="col-md-3 flex-center">

          <img src="https://mdbootstrap.com/img/Photos/Template/36.png" class="img-fluid wow fadeIn" data-wow-delay=".4s">

        </div>

        <!--/Third column-->

​

        <!--Fourth column-->

        <div class="col-md-3 flex-center">

          <img src="https://mdbootstrap.com/img/Photos/Template/37.png" class="img-fluid wow fadeIn" data-wow-delay=".2s">

        </div>

        <!--/Fourth column-->

​

      </div>

      <!--/First row-->

​

    </div>

  </section>

​

</div>