IM Pei, who began his long career designing buildings for a New York real estate developer and ended it as one of the most revered architects in the world, died on Thursday at his home in Manhattan. He was 102. His death was confirmed by his son Li Chung Pei, who is also an architect and known as Sandi. He said his father had recently celebrated his birthday with a family dinner. Best known for designing the East Building of the National Gallery of Art in Washington and the glass pyramid at the entrance to the Louvre in Paris, Pei was one of the few architects who were equally attractive to real estate developers, corporate chieftains and art museum boards. And all of his work – from his commercial skyscrapers to his art museums – represented a careful balance of the cutting edge and the conservative.