Neonates
Newborn animals.  For humans, it generally refers to the first four weeks of life.
Nephron
The functional unit of the kidney that produces urine. The primary areas are the glomerulus, convoluted tubule, and collecting duct.
Nephrotoxin
A systemic poison whose target is the kidney.
Non-polar
A term used to describe a molecule, which is neutral or possesses neither a positive or negative charge.