Tutsi (largest) and the Twa (smallest). Small numbers of Hema, Kiga and Furiiru people also live near the Tutsi in Rwanda. The Northern Tutsi who reside in Rwanda are called Ruguru (Banyaruguru), while southern Tutsi that live in Burundi are known as Hima, the Tutsis who resides in Masisi which is in Kivu and they are known as Banyamasisi and the Tutsi that inhabit the Kivu plateau in the Congo go by Banyamulenge. The definitions of "Hutu" and "Tutsi" people may have changed through time and location. Social structures were not stable throughout Rwanda, even during colonial times under the Belgian
Hutu of Rwandan national unity, but has been criticized as an attempt at historical revisionism. Still others suggest that the two groups are related but not identical, and that differences between them were exacerbated by Europeans, or by a gradual, natural split, as those who owned cattle became known as Tutsi and those who did not became Hutu. Mahmood Mamdani states that the Belgian colonial power designated people as Tutsi or Hutu on the basis of cattle ownership, physical measurements and church records. There is an ongoing debate as to whether the Hutu and Tutsi are really separate groups or not;