IMRAD is the most common format for structuring scientific articles. The acronym stands for Introduction, Method, Results and Discussion. In some versions, the A can also stand for Analysis.
The IMRAD format is used to write assignments on a number of natural science degree programmes. There may also be other requirements for the structure of your assignment, so check the academic regulations and ask your teacher before using the IMRAD structure for an assignment.
See an example of how to use the IMRAD structure in a scientific article.