Simplify the following text for a Grade 10 native English-speaking person.
Original: Today many of his piecesâ '' including his numerous self portraits , landscapes , portraits and sunflowersâ '' are among the world 's most recognizable and expensive works of art .
Simplified: Today , many of his pieces -- including his many self portraits , landscapes , portraits and sunflowers -- are some of the most famous and costly works of art in the world .