请找一下这段英语短文中的知识点
Cloning has two major uses.Fistly,gardeners use it all the time to produce commercial quantities of plants.Secondly,it is valuable for research on new plant species and for medical research on animals.Cloning plants is staightforward while cloning animals is very complicated.It is a difficult task to undertake.Many attempts to clone mammals failed.But at last the determination and patience of the scientists paid off in 1966 with a breakthrough-the cloning of Dolly the sheep.
词组，习惯用语，句型等。