The early history of humanoids was dominated by the work of Kato at Waseda University with his pioneering work on the WABOT-1 and in a more indirect way, Vukobratovic with his work on exoskeletons. Their ground-breaking work laid down many of the key principles of humanoid design and ambulation, which have been the basis of many robots up to the current time. Kato’s early humanoids used hydraulics as the primary actuation (due to the high power to weight performance needed in walking), but from the early Honda robots, the trend, particularly in Asia, was toward electric systems due to the improvements in electric motor power and control and perceived weaknesses in the control and operation of hydraulics. Nonetheless, the force control concept for humanoids was now recognized as an important upgrade, particularly with the expectation that humanoid robots would be required to physically interact with people in order to serve as intelligent assistants.