Renal agenesis. Renal agenesis is a medical condition in which one (unilateral) or both (bilateral) fetal kidneys fail to develop.
Polycrystalline cells are composed of multiple silicon crystals, which is a cheaper way to manufacture solar modules. Put simply, these cells are easier for a factory to produce, so they are less expensive. Polycrystalline cells are made by several methods, but most commonly with a cast of molten silicon.
A crystal of amethyst quartz. Microscopically, a single crystal has atoms in a near-perfect periodic arrangement; a polycrystal is composed of many microscopic crystals (called crystallites or grains); and an amorphous solid (such as glass) has no periodic arrangement even microscopically.