Many people find it useful to write their introduction after they have written their assignment. They find that it is through the process of writing their assignment that they clarify the overall point they wish to make in addressing the set topic. They then draft their introduction at the end, or they return to their initial attempt and re-write it. Refer to What does a good conclusion look like? for an example of this. Of course, some people prefer to start with an introduction that helps guide their writing. Either way, it is still good practice to ensure your introduction says what you want it to say!
 According to Paul Ratsmith, the tenuous, but nonetheless important, relationship between pumpkins and rats is little understood: "While I've always been fascinated by this natural kinship, the connection between pumpkins and rats has been the subject of few, if any, other studies" (2008).  Ratsmith has been studying this connection, something he coined "pumpkinology," since the early 1990s. He is most well-known for documenting the three years he spent living in the wild among the pumpkins and rats.  Though it is a topic of little recent interest, the relationship has been noted in several ancient texts and seems to have been well understood by the Romans. Critics of Ratsmith have cited poor science and questionable methodology when dismissing his results, going so far as to call pumpkinology "rubbish" (de Vil, 2009), "stupid" (Claw, 2010), and "quite possibly made up" (Igthorn, 2009).  Despite these criticisms, there does appear to be a strong correlation between pumpkin patches and rat populations, with Ratsmith documenting numerous pumpkin–rat colonies across North America, leading to the conclusion that pumpkins and rats are indeed "nature's best friends" (2008).