Trifidae are a family of seats consisting of three different armchairs, deriving from a single typological and formal origin. Consisting of three separate parts, the small easy chair, high backrest armchair and the enclosing lounge chair share the same triangulated form with the focal point in the central part, embracing the user’s lumbar area and functioning as an armrest. The tilting of the three parts of the armchairs resembles closing and openings of the petals of flower buds. Regardless to the fact that the easy chair differs in size and form from the others, while the armchair and the lounge chair share the same base and the armrest, all three are perceived as neighbouring elements in progressive series. The alternation of the backrest of two bigger chairs results in different characters of the objects. Application of the  enclosing backrest provides an introverted, expressive chair, protecting it’s user from his/her surrounding, while the use of the slim, high backrest ends up in an open, extrovert personality and usage of the chair.