The talk will deal with two themes. One is operator algebra of singular integrals with holomorphic kernels in different contexts, that have alternative formulations as the H-infinity functional calculus in the Fourier multiplier setting and the Cauchy-Dunfort functional calculus of Dirac operators in the functional anslysis setting. The second theme is Fueter's theorem in quaternionic analysis and its generalizations to Clifford anslysis. They
are necessary tools for the study of singular integrals in the first theme.