Pits were grown from the edges of thin 304 SS (stainless steel, SS) foils, and the resulting cavities were viewed by video microscopy, allowing the study of real-time pit growth under different applied conditions, e.g. potential and temperature. This method also allowed direct comparison of the current recorded with the development of the pit. All pits developed a lacy metal cover, which was shown to provide a diffusion barrier necessary to sustain stable pit growth, especially in the early stage of a pit's life. Pit growth, morphology and cover formation are explained with the help of a semi-quantitative model based upon concentration gradients and active/passive transitions. Pits grown in plate material and high alloy stainless steel have the same basic morphology.