how to arrange height of grid system in bootstrap

boot strap grid system is very useful and nice. but cells height can not arrange in default. ex. following image does not arrange three images height. one way to solve it, write display:flex in div wrapping some cells. <div style=”display:flex”> <div class=”col-md-4″></div> <div class=”col-md-4″></div> <div class=”col-md-4″></div> </div> cells become arranging. but above way are not…