Studies of the solid-phase nucleation of molten 3-methoxy-4-hydroxybenzaldehyde (vanillin) were performed either on bulk (a few cubic millimeters) or on emulsified (cubic microns) samples. The results obtained from macroscopic observations and differential scanning calorimetry have pointed out undercooling phenomena characterized by roughly the same order of undercooling degrees Delta T = T-m - T-s (T-m, melting temperature; T-s, the most probable solidification temperature) for steady cooled (-3 degrees C/min) bulk and emulsified samples, namely, Delta T approximate to 43 degrees C. At a fixed temperature, the solidification of the dispersed droplets can be described by an S-shaped curve that has been interpreted in terms of a polynuclear mechanism. Finally, the decrease of the undercooling degree exhibited after a solidification-melting process has been explained by the formation of nucleating sites at the liquid-emulsifying medium interface.