And they’re an important part of Passover today: Traditionally, a hard-boiled egg is placed on the Seder plate as a symbol of renewal and the cycle of life. Some Jewish families serve hard-boiled eggs dipped in salt water at the start of the Seder meal in commemoration of the tears of Jewish slaves in ancient Egypt.

Jews weren’t the only ones who understand the value of eggs; they’ve been eaten around the world for millennia. The ancient Egyptians were great lovers of eggs, which they liked to boil, poach, and use in sauces, breads, and pastries. In ancient Greece, eggs were considered a symbol of life and rebirth and were used in fertility rites during the spring equinox. (Many Greek philosophers, including Pythagoras, abstained from eating eggs, however, as they considered them to be a symbol of the world and the four elements; they claimed the shell represented the earth; the yolk, fire; the egg white, water; and there was air under the shell.) The ancient Romans used eggs to make custards, omelettes—especially ova spongia ex lacte, an omelette with milk, honey, and black pepper—fried eggs (ova frixa), and soft-boiled eggs, which were often served with a sauce made from pine nuts, lovage, pepper, vinegar, honey, and liquamen (fish sauce).

After the fall of the Roman Empire, eggs were less used in cookery—except in Spain, where they became a staple food of Sephardic Jews. Eggs (called huevos in Ladino) were made into all kinds of fritadas (baked omelettes), vegetable cazuelas (casseroles), and stuffings. They were also roasted over hot coals and sprinkled with parsley and vinegar (huevos asados) or slowly cooked overnight in their shells with onion skins until the whites were light brown to become huevos haminados, which were traditionally served for the Sabbath and for Passover. Hard-boiled eggs were commonly served at Jewish funerals; according to the Kol Bo, a collection of Jewish laws and rituals published in Naples in 1490, eggs were “symbolic of the roundness of the world and the mourning which comes to us all.”

By the 15th century, eggs had become an important food for Ashkenazi Jews. At that time, most Eastern European Jews had a chicken coop to keep them well-supplied with eggs. They were used to make all kinds of dishes, from challah, eier mit zwiebel (scrambled eggs and onions), and chopped liver to lokschen (egg noodles), kneidlach (matzo balls), and all kinds of sweet and savory kugels, cakes, and pastries. Hungarian Jews were especially fond of Zsido tojas (literally, Jewish eggs): hard-boiled eggs stuffed with grated onion, butter, and mustard. A similar dish was made by Polish Jews, but with sour cream instead of butter.

Mizrahi Jews in the Middle East use eggs more sparingly. They are used to make a variety of small vegetable omelettes or fritters, scrambled eggs, pancakes (atayef), cakes, and pastries. They also like to prepare beddah b’lemuneh—an egg and lemon sauce usually served with rice or stuffed onions. In Israel, they are very fond of the North African shakshuka—eggs cooked on a bed of tomatoes, simmered with onions, peppers, and spices.

In Jewish tradition, it is said that eggs are symbolic of Jewish history as well as a symbol of life and death and fertility because they are the only food that becomes harder when cooked, while the shells remain sturdy, yet fragile. For this reason, eggs are often served on solemn occasions like fasts and meals before funerals.

Different kinds of eggs are used in different parts of the world. For the Chinese, the egg is not just a food, but a significant cultural symbol representing both yin—which represents the egg yolk and the female principle of darkness, passivity, absorption, the color orange, and the earth—and yang: the egg white, which is conceived as male energy, heaven, light, and penetration. The uniting of yin and yang brings a balance of the Confucian five virtues of truth: wisdom, righteousness, propriety, faithfulness, and benevolence.

Although the Chinese eat chicken eggs, they are also partial to eggs from pigeons, ducks, geese, and quail, which they prepare in a variety of ways not found in the West, like tea eggs or marbled eggs—which are slightly cracked, then boiled in a spiced, tea-based broth that gives them a marblelike pattern—and of course the famous hundred-year-old eggs, which have green whites and dark gray yolks and are, in fact, closer to 100 days old. Quail eggs are widely used in Thailand, Vietnam, and the Philippines. In the early part of the 20th century, alligator eggs were widely eaten in the Southern United States. Currently, ostrich eggs—which are more than 20 times the size of chicken eggs—are considered a luxury food, but if you want to try them, remember to allow sufficient time for cooking, as an ostrich egg can take between 60 and 90 minutes to boil. Alternatively, you can scramble an ostrich egg in 20 to 30 minutes.

Eggs have always been an important staple food as they are complete protein and contain all nine essential amino acids. They are rich in vitamin A, vitamin D, vitamin B2, and vitamin B12, as well as minerals such as iron, selenium, zinc, iodine, and choline, which is good for brain function. They are also a good source of antioxidants, especially lutein and zeaxanthin, which are good for the health of your eyes.

It is often said that a chef’s ability can be measured by how he boils an egg. To make hard-boiled eggs, some cooks recommend placing an egg in a pot of warm water, bringing it to a boil, covering it, then turning off the heat and leaving it to sit for 10 minutes. Others suggest lowering the egg into boiling water for half a minute, adding ice cubes, then simmering for 11 minutes. But if these methods don’t turn out well for you, do not worry, you can always “un-boil” your egg. According to Herve This, in his book Molecular Gastronomy: Exploring the Science of Flavor, you can “un-cook” your egg by adding sodium borohydride, which causes the protein molecules in the egg to detach from each other. This enables the egg to return to its liquid form in less than three hours. If you don’t have borohydride at hand, vitamin C apparently works just as well.