How the relative length of the CSS differs between REM and EM

rem vs em

As the relative length unit of two, are based on a multiple relationship length, but the reference is not the same, here the case analysis of the difference between the two:
1,em reference Multiples object is its own font size, font-size, if not inherited upward;
2,rem The reference multiplier object is the root element

Case code:

 

Use:
If you are multiplying the size of the parent element, you can select EM as the unit.
REM is often developed on the mobile side, and is a great choice to solve the situation of the display under different screens, followed by how to use 100% layout and REM to develop mobile business.