Structure and development of Populus tremula L. leaf are examined. The data of the microrelief fold initiation time in different parts of its epidermis are given. During the first phase of leaf growth the folds begin to develop above the veins and near the stomata, and on the basic epidermal cells - during the second phase. It is shown that the elements of folded microrelief appear at the surface of lower epidermis in the period, when the division and expansion of its cells, and also the differentiation of stomata are still in process.