8th weeks
- The embryo measures 13 mm (1/2 inch) in length.
- Lungs begin to form.
- The brain continues to develop.
- Arms and legs have lengthened with foot and hand areas distinguishable.
- The hands and feet have digits, but may still be webbed.
- The gonadal ridge begins to be perceptible.
- The lymphatic system begins to develop.
- Main development of external genitalia starts.