These animals grow to between 7.5 and 9 cm in length and as adults can weigh 25-43 grams. They live two to three years on average. A Chinese hamster's body proportions, compared with those of other hamsters, appear "long and thin" and they have (for a hamster) a relatively long tail. Males have a relatively large scrotum, therefore females are generally kept as pets and males are used solely for breeding and research purposes. Chinese hamsters are not related to the social "dwarf" hamsters. The term "dwarf" is often used to refer solely to animals in the genus Phodopus, (the two types of Russian Dwarf Hamsters and Roborovskii Dwarf Hamsters).
The wild colour is black with brown lines above with a black stripe down the spine and a whitish belly. This coloration, combined with their lithe build and longer tail, makes them look "mousy" to some eyes and, in fact, they are members of the group called ratlike hamsters. Besides the wild colour, a well-known variation is the white-spotted Chinese hamster, which often is grayish white all over, with only a dark stripe on its back. They have quiet temperaments and are easily handled; one of their endearing traits is that of clinging to a finger with all four paws, rather like a harvest mouse on a corn stalk. Chinese hamsters can be quite nervous as youngsters but, once they are tame, display an endearing calmness and gentleness of character.
In the past, Chinese hamsters were commonly used laboratory animals, until they were replaced by the common mouse and rat, which are easier to keep and breed; however, quite a few biotech drugs are still being produced by putting the gene for the protein into Chinese hamster ovary cells (CHO cells), which then produce the protein.
Of note, some US states such as California regard the Chinese hamster as a pest, and as a result require a special permit to own, breed or sell. (wiki)