Four popcorn morphologies have been described but an account of the sizes and shapes that each morphology had during hot-air popping have not been reported. In this work, high-speed videos of popping kernels were captured to study two-dimension (2-D)morphometry changes during hot-air popping. Six main observed geometries during popping were: initial kernel, kernel with incipient expanded pericarp, kernel at the onset of the popping, splitting of the endocarp, formation of appendages and, the developed flake, in such a way as to allow the definition of 5 stages during popping (one stage between each one of the above geometries). Total duration for the formation of each morphology was 0.480, 0.344, 0.140 and 0.343 s for mushroom, unilateral, bilateral and multilateral flakes respectively. Projected area and perimeter increased due to the expansion of the kernel, circularity decreased since the flakes showed a decrease in roundness and smoothness and, on the other hand, the solidity, also decreased due to the decrement of smooth lines in the outside boundary of the flake. It is noteworthy that the two parameters (circularity and solidity)dropped following the same sequence during popping and that the main difference among geometries was the time taken to pop.