Sensei Morihei Ueshiba (1883-1969) defined the principles of Aikido in 1929 (approximately 50 years after the creation of Judo in 1852) by integrating human moral values into the purely physical techniques of the traditional martial arts.
The practice of this non-competitive discipline does not have a final objective of destroying ones adversary, nor dissuasion by fear, but an exchange of energy intended to diffuse the aggression and move out of the conflict situation.
The Aikidoka primarily uses avoidance in order to avoid collision; he guides the attack of his opponent, by controling him, until a point of imbalance is reached. At this moment, the Aikidoka chooses either to throw or immobilise his adversary depending on the physical effort needed for one or the other, and in accordance with the energy deployed and the desired level of efficiency.
Since Aikido does not require any particular level of physical strength, it can be practiced by everybody; child or adult, man or woman.