Dragon eggs can be identified by their size alone. Some reach the height of a man's shoulder. Dragons are in the eggs for at least several months, with some incubating for 10 years. Each breed has a different type of eggshell. Although according to Sir Edward Howe, Chinese breeds are notoriously hard to categorize. Most of them have an appearance similar to porcelain.
In the wild eggs are buried under volcanoes and hot springs to keep them warm, but domesticated eggs are usually kept in warm places. In the early 19th century examples include like the a furnace for heating a sauna or steam room at the Sultan's palace in Istanbul, and under the heated courtyard at Loch Laggan covert in Scotland.
Dragons learn language while within the shell. Temeraire is unusual in acquiring three languages - Chinese, French and English - in this way, but most dragons are hatched knowing at least one draconic or human language. Once the egg is sufficiently mature, usually indicated by the hardness of its shell, the dragonet inside is able to understand what is being said around it. Care must be taken at this point. For example, if the dragonet is frightened in the shell by what it overhears, it will often turn out to be a timid dragon. The dragonet's interest in the conversations it overhears, combined with the complete lack of interesting events inside the shell, gives the dragonet motivation to hatch.
Some African tribes believe that the spirits of departed ancestors are reincarnated as dragons. This reincarnation is achieved through the methods used to care for Dragon eggs. Through a series of rituals and chanting, the egg is exposed to the beliefs and actions of a revered individual who has recently died. When the egg hatches these "memories" have become the dragon's own and they regard them selves as the same person as the departed spirit that has been "called" to their egg. This is also why the humans, who are part of those tribes, refer to dragons as ancestors and the dragons, who took part in this ritual, think of them as their children.