  Formation of isolated chiral skyrmions by homogeneous and heterogeneous
nucleation has been studied in thin layers of cubic helimagnets via elongation
of torons and chiral bobbers, correspondingly. Both torons and bobbers are
localized in three dimensions, contain singularities, and according to the
theoretical analysis within the standard phenomenological models can exist as
metastable states in saturated and modulated phases of noncentrosymmetric
ferromagnets. Their elongation into the defect-free skyrmion filament is
facilitated by small anisotropic contributions making skyrmion cores negative
with respect to the surrounding parental state. We show that isolated magnetic
torons pose the same problem of compatibility with a surrounding phase as the
torons in confinement-frustrated chiral nematics [I. Smalyukh et al., Nature
Mater 9, 139-145 (2010)]. We underline the distinct features of magnetic and
liquid-crystals torons and calculate phase diagrams indicating their stability
regions.
