Dress
Unlike many Middle Eastern countries, the dress in Iran for women is often times bright and colorful, which makes it impossible to miss a Persian in the region. The women dress in a more traditional style, while the men tend to prefer western-styled clothing, which is often times in browns and earth-toned colors, making their dress quite a contradiction to that of the women.
Today the dress is varied significantly as women tend to wear brightly colored loose-fitting clothing, but many of the more conservative Muslims prefer to wear a black dishdasha or abaya. This loose-fitting clothing reveals nothing and many women who do wear this tend to also wear a hijab over their heads and often times will also cover their faces. In fact, women must cover their hair by law in Iran, although many young people reject this notion (although not publicly). Even for the women in more colorful dress, it is loose-fitting and conservative as all skin is covered to the hands and feet. Men in Iran have significantly shifted to conservative western-styled clothing, but this is not consistent across the country. Many men continue to wear more traditional clothing items, including the dishdasha.
As a visitor to Iran you are likely on a tour, so check with your tour company for the most recent recommendations on travel to the country. However, some things that haven't changed in some time is the conservative nature of dress in the country. Always cover your arms and legs in Iran and women must always cover their hair by law. Also avoid anything that may indicate where you are from or that may encourage social unrest. Although wearing a shirt with a flag of a foreign country or a foreign country's soccer jersey (football kit) may seem innocent in Iran it can be interpreted very differently and may send you to prison or get you deported.