Conversion of Simple sentences to Complex

A Simple sentence can be converted to a Complex sentence by expanding a word or
phrase into a Subordinate clause.
This clause may be a Noun, Adjective or Adverb clause.
Simple. -- He confessed his crime.
Complex. -- He confessed that he was guilty.
Simple. -- His silence proves his guilt.
Complex. -- The fact that he is silent proves his guilt.
Simple. -- He bought his uncle's library.
Complex. -- He bought the library which belonged to his uncle.