Human embryo. Illustration of a 32-day-old human embryo. At 32 days the embryo is not yet recognisably human and measures only around 6mm in length. The developing ears appear as pits (upper centre) and rudimentary eyes develop in the form of stalks. The nose and mouth will develop from the folds in the neck. Below the neck is the heart bulge; at this stage the immature heart already produces a form of heartbeat. Rounded buds form the beginnings of arms and legs and internal organs are growing. The back grows more rapidly than the front in the young embryo, giving it a C- shape and a conspicuous tail.