Aikido was originated by Master Morihei Uyeshiba, who instructed only to carefully selected students, requiring the highest references.
Master Uyeshiba, Known throughout the Aikido world as O'Sensei, studied the Japanese Martial Arts of Kito Ryu, Aioi Ryu, Daito Ryu AikiJitsu, JuJitsu, the Bayonet arts, Kendo, Kudo, Bojitsu and many others. Aikido was created by him in the the 1930's.
O'Sensei was such a formidible and effective martial artist, that he attracted students from all over Japan, including senior students of Kodokan Judo who were sent to him by Jigaro Kano Sensei, the creator of modern Judo.
Before the 2nd World War, Aikido was not taught to the general public and only to carefully selected students requiring the highest references.
After the War however, the creator of Aikido decided that it should be spread throughout Japan and the World.
O'Sensei died in 1969 at the age of 88. His son Kisshomaru Uyeshiba took his place as the second Headmaster of Aikido.
This was also when the Art of Aikido began to split into several sub-schools of the art. The Uyeshiba school known as the hombu, is still regarded as the principal school of Aikido.
The other schools, started by students of O'Sensei, place emphasis on different aspects of the rich heritage of this sophisticated art.
Yoshinkan Aikido, developed by Gozo Shioda, one of O'Sensei's early students emphasises the Martial aspect of the art.
Tomiki, Aikido attempts to add a sporting dimension to Aikido, in a similar way to modern Judo. This was developed by Kenji Tomiki, a talented Judo master asked by Jigaro Kano - the founder of Judo to study Aikido.
Ki Aikido was developed by Koichi Tohei, formerly the Chief Instructor at the Hombu, and emphasises the spiritual side of Aikido.
There are a few other smaller groups but the majority of Aikido today is contained in the above groups.
After the death of Kisshomaru Uyeshiba in 1999, the place of Doshu (headmaster) was taken by Moriteru Uyeshiba, the grandson of the founder.