Who was the writer for the episode called "What Are You Made of?"
CREATE TABLE "table1_23399481_3" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_in_millions" text
);
SELECT "written_by" FROM "table1_23399481_3" WHERE "title"='\"What Are You Made Of?\"';