Nowrūz, meaning 'New Day' is the traditional ancient Iranian festival and also the start day of Iranian "New Year".
Nowruz is celebrated and observed by Iranian peoples and the related cultural continent and has spread in many other parts of the world, including parts of Central Asia, South Asia, Northwestern China, the Crimea and some ethnic groups in Albania, Bosnia, Serbia and the Republic of Macedonia.
Nowruz marks the first day of spring and the beginning of the year in Iranian calendar. It is celebrated on the day of the astronomical vernal equinox, which usually occurs on March 21 or the previous/following day depending on where it is observed.
The moment the Sun crosses the celestial equator and equalizes night and day is calculated exactly every year and Iranian families gather together to observe the rituals.
Nowruz was originally a Zoroastrian festival, and holiest of all, and as such has unclear date of origin but was "probably" invented by Zoroaster himself. Since the Achaemenid era the official year has begun with the New Day when the Sun leaves the zodiac of Pisces and enters the zodiacal sign of Aries, signifying the Spring Equinox.
The UN's General Assembly in 2010 recognized the International Day of Nowruz, describing it a spring festival of Persian origin which has been celebrated for over 3,000 years. Since 2010, the United Nations General Assembly recognizes March 21 as the "International Day of Nowruz".
In association with the "rebirth of nature", extensive spring-cleaning is a national tradition observed by almost every household in Iran. This is also extended to personal attire, and it is customary to buy at least one set of new clothes. On the New Year's Day, families dress in their new clothes and start the twelve-day celebrations by visiting the elders of their family, then the rest of their family and finally their friends. On the thirteenth day families leave their homes and picnic outdoors.
During the Nowruz holidays, people are expected to visit one another in the form of short house visits, which are usually reciprocated. Typically, on the first day of Nowruz, family members gather around the table, with the Haft Seen on the table or set next to it, and await the exact moment of the arrival of the spring. At that time gifts are exchanged. Later in the day, the first house visits are paid to the most senior family members. Typically, the youth will visit the elders first, and the elders return their visit later. When in previous year, a family member is deceased; the tradition is to visit that family first (among the elders). The visits naturally have to be relatively short; otherwise one will not be able to visit everybody on their list. A typical visit is around 30 minutes, where you often run into other visiting relatives and friends who happen to be paying a visit to the same house at that time. Because of the house visits, you make sure you have a sufficient supply of pastry, cookies, fresh and dried fruits and special nuts on hand, as you typically serve your visitors with these items with tea or sherbet.
Haft Sīn or the seven 'S's is a major tradition of Nowruz. The haft sin table includes seven specific items starting with the letter 'S' or Sīn in the Persian alphabet. The items symbolically correspond to seven creations and holy immortals called Amesha Sepanta protecting them. The seven elements of Life, namely Fire, Earth, Water, Air, Plants, Animals, and Human, are represented. They also have Astrological correlations to five planets Mercury, Venus, Mars, Jupiter, Saturn, and Sun and Moon. With the advent of Islam the word Amesha Sepanta shortened to and eventually was remembered by just the letter S and the number 7. Traditionally, families attempt to set as beautiful a Haft Sīn table as they can, as it is not only of traditional and spiritual value, but also noticed by visitors during Nowruzi visitations and is a reflection of their good taste.
The Haft Sīn items are:
• Sabzeh - wheat, barley or lentil sprouts growing in a dish - symbolizing rebirth
• Samanu - a sweet pudding made from wheat germ - symbolizing affluence
• Senjed - the dried fruit of the oleaster tree - symbolizing love
• Sīr - garlic - symbolizing medicine
• Sīb - apples - symbolizing beauty and health
• Somaq - sumac berries - symbolizing (the color of) sunrise
• Serkeh - vinegar - symbolizing age and patience
Other items on the table may include:
• Sonbol - Hyacinth (plant)
• Sekkeh - Coins - representative of wealth
• traditional Iranian pastries such as baghlava, toot, naan-nokhodchi
• Aajeel - dried nuts, berries and raisins
• lit candles (enlightenment and happiness)
• a mirror (symbolizing cleanness and honesty)
• decorated eggs, sometimes one for each member of the family (fertility)
• a bowl of water with goldfish (life within life, and the sign of Pisces which the sun is leaving). As an essential object of the Nowruz table, this goldfish is also "very ancient and meaningful" and with Zoroastrian connection.
• rosewater, believed to have magical cleansing powers
• the national colours, for a patriotic touch
• a holy book (e.g., the Avesta, Qur'an, Bible, Torah, or Kitáb-i-Aqdas) and/or a poetry book (almost always either the Shahnama or the Divan of Hafez)
(Quoted from the Wikipedia)
Sabzeh 
