For any complex quadratic map p_c(z)= z^2 + c, which has a finite critical orbit, the structure of the Julia set can be well-understood combinatorially by means of a finite tree, connecting the postcritical points: the Hubbard tree. For example, one can study kneading theory (=symbolic dynamics) this way. In this talk I want to address the `reverse' question of constructing the Hubbard tree starting from the kneading sequence. In other words, given a (pre)periodic 0-1-sequence $\nu$, how can one construct a tree with a single critical point, and at most two-to-one dynamics, such that the itinerary of the critical point is exactly $\nu$? Interestingly, there exist such trees that don't correspond to any quadratic polynomial, which leads us to the so-called complex Admissibility Condition - the complex version of the Admissibility Condition for real map, dating back to Milnor and Thurston monograph from the early 1980s.