In this chapter, we covered the most important aspect of Bootstrap. We learned how Bootstrap's grid system operates, gaining an understanding of its many features. We have seen how we can leverage Bootstrap to manage responsive images, as well as how to target specific content to specific displays. On top of that, we have learned how to use the extremely useful Bootstrap helper classes. We also discovered a very nice feature of all the layout specific utility classes: the fact that they can also be used as mixins, and are indeed used as mixins within other Bootstrap classes. Leveraging these classes when we start writing custom style rules for MyPhoto will surely come in useful. As such, our understanding of Bootstrap is now quite deep, so let us go forward to the next chapter and build the layout for our MyPhoto page.