New and emerging virus species are becoming an increasing threat to our way of life economically and physically. Plant viruses are particularly significant as they affect our food supply and are capable of rapidly spreading to new plant species. Geminiviruses are a group of viruses that highlight this phenomenon well. Indeed Geminiviruses are some of the earliest recorded plant viruses being described as far back as 752 AD in a Japanese poem written to describe geminivirus symptoms in eupatorium leaves (Saunders et al.,2003). More recently, and in a more threatening manner, Geminiviruses have adapted to infect key crop species such as maize, sugarcane, tomatoes, beet and many more. An example of this is the introduction of grasses such as Maize into Africa, which allowed a species jump for mastreviruses, which were endemic in native grasses (Varsani et al.,2008a). Over a relatively short period of evolutionary time a number of new Geminiviruses have emerged, making them a good model for understanding the evolution and spread of new plant pathogens. The economic importance of Geminiviruses also makes an understanding of their mechanisms of adaptation crucial in preventing new emergence and minimising the impact of current strains.