.person__face {}
 inside of .person--handsome {}
; instead, we make use of {{or: LESS | Sass}}’ parent selectors to prepend .person--handsome onto the existing .personface {} selector. This means that all of our .personface {}-related rules exist in once place, and aren’t spread throughout the file. This is general good practice when dealing with nested code: keep all of your context (e.g. all .person__face {} code) encapsulated in one location.