EDITORIAL INTRODUCTION TO CLIFFORD ANALYSISComplex numbers were invented to answer a purely mathematical question. But before he discovered the quaternions, W.K. Hamilton was looking for a possible algebra structure for the three-dimensional (3D) physical space. Behind it is the Platonic idea that the physical reality would be the o print of a 'more perfect mathematical reality', which also means that physical problems can be modelled using mathematics and conversely, the modelling of physical problems leads to the discovery of interesting new mathematics. But the Platonic world of mathematics is also di erent from the real world and since Einstein we know that the physical space (or space-time) tends to behave not like a vector space or algebra but like a manifold with a weaker and hence more general structure. In the same way, the mathematical description of physical phenomena often needs the more general non-linear mathematics. But in spite of this, also the more restrictive and special mathematical structures like algebras may be quite useful for the applied sciences. Hereby we ÿrst of all mention the wide scope of applications of complex algebra and analysis and also of the quaternion algebra H = {q 0 + q 1 I + q 2 J + q 3 K : q 0 ; q 1 ; q 2 ; q 3 ∈ R} with its deÿning relations IJ = − JI = K; JK = − KJ = I; KI = − IK = J It namely allows the deÿnition of the so-called Fueter operator (already discovered by Hamilton) @ q = @ q0 + @ q1 I + @ q2 J + @ q3 K which may not be deÿned on the 'physical 3D-space' but does contain as a restriction the Moisil-Teodorescu operatorwhich has applications in electrostatics and magnetostatics. More so, after replacing the real co-ordinate q 0 by the imaginary i t; t meaning the time, the Fueter operator transforms into a kind of quaternion Dirac operator which has as null-solutions special source free solutions of the Maxwell ÿeld. Later on, still led by the idea to mathematize physical space, people looked for algebras which did not coincide with e.g. the physical space but were at least generated by it, more, in general, they were looking for algebras generated by a general m-dimensional space. To this class belong ÿrst of all the Grassmann algebra with deÿning relations f j f k = − f k f j