Sass is written in Ruby, and so we need Ruby installed on our computers. To download and install the latest version navigate to Ruby's official site: https://www.ruby-lang.org/en/downloads/. To find out if you already have Ruby installed on your machine, run this command on your command line or Terminal: $ ruby -v.

If Ruby is installed, the output will display the version number. For example, the output in my Terminal when I execute $ ruby -v is ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-darwin16]. Any version from 2.3 onward is more than good enough for our purposes.