The Cathedral Engineers: Shot on location in France and New York City, the program looks at the history and philosophy of European gothic cathedrals. Neem: A Natural Insecticide: Products of the neem, one of the world's most useful trees, are used to make everything from soap to insecticide. Bluebird Trails: Pushed out of prime nesting sites by the introduction of the english sparrow and starling in 1900, the North American bluebird is making a comeback thanks to specially constructed bluebird boxes built across eastern North America.