Suppose that a Legendrian knot Λ in the standard contact space J 1 (R) (or J 1 (S 1 )) can be defined by a generating family F : R × W → R (or F : S 1 × W → R). Applying to the generating family F one-parametric version of Morse theory, we construct certain combinatorial structures on the wavefront of Λ. These structures, in particular provide invariants of Legendrian knots.