After three movies and six suits which had all effectively used the same helmet, it was decided that with Iron Man 3 it was time for an update that reflected the growth of Tony Stark, 5 years older and weathered by the events of Avengers. The helmet would need to show both technological advancement and maturity. Tony's arc has always been toward more vulnerability and humanity, so it seemed appropriate to incorporate more anatomical elements into the design, beginning with suggesting the frontal bone of the cranium between the forehead intakes, and replacing the circular "ear muff" with a more integrated intake/ear shape that continues the crease of the cheekbone. It was also important to reflect Tony's inner conflict, so I introduced tension into the "masseter muscle" form that suggests a clenched jaw, as well as adding cutlines in the forehead that mirror frown lines.