A quaternion is a type of hypercomplex number, that is a generalization of complex numbers to more than two dimensions. Quaternions have four components: one real, and three imaginary. Another way of representing this is to say that they are complex numbers with a vector imaginary part. The quaternions were discovered by Sir William R. Hamilton in Dublin in 1843. They led to the development of vector methods, but subsequently became neglected. Today they are used in robotics, aeronautical engineering and generally in fields where 3-dimensional calculations have to be computed.