We have examined the critical nucleus through density functional calculations of crystalline fluctuations in a Lennard-Jones fluid. The free energy functional we employ has a square-gradient form, with the parameters for a Lennard-Jones interaction potential determined by a modified weighted density approximation applied locally through the Liquid-solid interface. We have found that the interface and the center of the critical nucleus behave differently at large undercoolings and at large superheatings. At large undercoolings, the interface of the critical nucleus sharpens, in contrast to the critical nucleus near the spinodal (at large superheatings) that is wide in extent and small in amplitude. We compare the radius and work of formation from classical nucleation theory to that from density functional calculations.