The American foundation of this cat breed was laid by the cats Siegfried (1984) and Brunhilde (1985). Cora Cobb, the owner of Siegfried and Brunhilde, was very impressed by the beauty of her blue/grey cats. Siegfried and Brunhilde looked like a Russian Blue but with a semi-long coat. To find out if it was possible to start a new breed with these cats, Cora got in touch with the geneticist of the American Cat Association. This geneticist, Dr. Solveig Pfleuger, said that the breed was best defined as semi-long haired Russian Blue. Supported by Dr. Pfleuger, Cora Cobb wrote the breeding standard according to the blue Russian, but with a difference: its coat length.
The International Cat Association (TICA) was the first association to recognize the Nebelung and provides the breed standard. The goal of the Nebelung breeding program is to produce a blue cat with the same type as those imported from Russia in the nineteenth and early twentieth centuries and to combine this type with a thick shimmering coat of medium length. The body and tail are long, the ears large in proportion to the head, and the eyes range in color from yellowish green to green. Size is medium and the body well-muscled. The coat is medium long on the body and longer on the tail, with lighter colored guard hairs. The overall appearance is long, sturdy and well muscled.