Developing vertebrate limb is a model system frequently used to study tissue differentiation and patterning. Research methods based on sophisticated genetic and molecular embryology techni- ques allowed revising some of the longstanding hypotheses in this field of research. One of them proposed the mechanism of limb development along proximal-distal axis based on the existence of Progress Zone. Recent results propose an alternative model of limb differentiation along this axis, so called Predetermination Model. Additionally, an unexpected function of sonic hedgehog in the determi- nation of digit number and identity was recently proposed. Some of those findings will be discussed in this article.