Edit in JSFiddle

(function($) {

    $(document).ready(function() {

      $('.wrap:nth-of-type(1)').addClass('activElem');

      $(window).scroll(function () {
        
        function isScrolledIntoView(elem) {
          var elementTop = $(elem).offset().top;
          var elementBottom = elementTop + $(elem).outerHeight();
          var viewportTop = $(window).scrollTop();
          var viewportBottom = viewportTop + $(window).height();
          return (elementBottom > viewportTop && elementTop < viewportBottom);
        }
        
        $('.wrap').each(function(){
          if (isScrolledIntoView(this) == true) {
            $(this).addClass('activElem');
          } else {
            $(this).removeClass('activElem');
          }
        });
      
      });	 
        
    });
})(jQuery);
<main>
  <div class="wrap">
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, 
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
  </div>
  <div class="wrap">
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, 
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, 
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry.
  </div>
  <div class="wrap">
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, 
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry,
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
  </div>
  <div class="wrap">
    Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, 
    when an unknown printer took a galley of type and scrambled it to make a type specimen book. Lorem Ipsum is simply dummy text of the printing and typesetting industry. 
    <a href="https://alextade.me/">alex tade artist</a>.
  </div>
</main>
*{
    margin: 0;
    padding: 0;
}
.wrap{
    padding: 150px 50px;
    text-align: center;
    overflow: hidden;
    position: relative;
    color: #fff;
}
.wrap::before{
    content: " ";
    display: block;
    width: 0;
    height: 0;
    transition: all 2s ease-in-out;
    border-radius: 50%;
    background-color: lightskyblue;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%); 
    z-index: -10;
}
.wrap.activElem::before{
    width: 150%;
    height: 150%;
}
.wrap:nth-of-type(2)::before{
    background-color: lightgreen;
}
.wrap:nth-of-type(3)::before{
    background-color: lightcoral;
}
.wrap:nth-of-type(4)::before{
    background-color: lightslategray;
}