Binary fission, meaning "division in half", refers to a method of asexual reproduction. It is the most common form of reproduction in prokaryotes and occurs in some single-celled eukaryotes. After replicating its genetic material, the cell divides into two equal sized daughter cells. The genetic material is also equally partitioned, therefore, the daughter cells are genetically identical (unless a mutation occurred during replication) to each other and the parent cell. They then split into two. Transverse binary fission divides the cell across the short axis (e.g., most bacilli-shaped bacteria), longitudinal binary fission across the long axis (e.g., Trypanosoma), and random binary fission across no defined axis (e.g., Amoeba). Some biologists use this term for multi-cellular organisms that asexually reproduce by dividing into two (e.g., some star fish). This is also known as fragmentation. Spirogyra, a type of algae also reproduces by binary fission.
For better understand of binary fission refer to Trypanosma division