Tree frogs (Hylidae and Litoria) jumping from branches to branches don't fall so long as toe pads make good contact with the trees, which indicates that they have strong adhesion ability (Fig. ). The sample preparation processing of tree frog's toe pads is as follows. The tree frog, Hylidae and Litoria, obtained from a local supplier, was raised in a terrarium and fed with crickets and water regularly. After euthanatizing the tree frog with MS-222, we cut the toe specimens and cleaned them with 0.67% SPSS, then immersed them into 2% PFA+2.5% glutaraldehyde solution for 48 hours. After that, we washed the specimens with 0.1 mol/L phosphate-buffered solution three times for each time lasting 15 min and dehydrated them in graded ethanol. The specimens were finally dried in a Critical Point Dryer (EM CPD300). A scanning electron microscope (SEM) was used to observe the surface morphology of the tree frog's toe pads. As shown in Fig. and Fig. , the tree frog's toe pads surface can be extracted into micro-level pillar arrays. The micro-level pillars are approximately polygons with diameter, channel width and height of about 10, 0.5 and 5 𝜇𝑚. All the animal protocols were approved by the Biological and Medical Ethics Committee of Tsinghua University.