This is a high magnification (40x) photograph of the kidney’s proximal and distal convoluted tubules. It was taken with an iPhone 4s. There are three ways to distinguish between a proximal convoluted tubule and a distal convoluted tubule. Firstly, the two structures differ in diameter – the proximal tubule contains a larger diameter than the distal tubule. The proximal tubule epithelium contains a brush border, whereas the epithelium of distal tubules contain a very few, short microvilli. Finally, the proximal tubule’s lumen is irregularly shaped (star-shaped), whereas the distal tubule lumen is typically smooth and almost perfectly circular.