Image
In this example, initially loaded small picture 375x500, continue using media queries for different screen sizes loaded big pictures.
medium.jpg - 0 to 768px
large.jpg - 768px to 1200px
extralarge.jpg - from 1200px
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Neque, dicta, quas fugit pariatur non similique reiciendis at. Culpa, libero, delectus, blanditiis ut aspernatur numquam voluptatum quas veniam veritatis illum error.