CREATE TABLE "table1_29897962_1" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_million" text
);

Question: Who directed the episode that had 3.55 million viewers?
SQL: SELECT "directed_by" FROM "table1_29897962_1" WHERE "u_s_viewers_million"='3.55';