Step1: Greetings.
Step2: Lead-in
Science is developing so fast that sometimes it is beyond our imagination. Man has created many things such as Radios, TV sets and so on. Do you think so?
What else has been created by man? Could you give us some examples?
(此处教师可以通过问题或简单的事例过度到我们本节课的话题cloning上面来。)
