  We review the relation between the "embedding" formalism and spinorial
projective space. The latter is more convenient when treating spin (and
indispensable for supersymmetry), as it maintains manifest conformal symmetry
while using 4-dimensional indices on fields/operators. It does this by solving
all algebraic constraints using 6-dimensional (off-shell) twistors. In an added
note we review the supersymmetric generalization, and give some new results for
N=3.
