It takes 21 days from the time when the queen lays the egg until a worker bee is born. Three days from laying the the egg hatches into a larvae and is feed royal jelly produced from the glands in the adult bees head. Two days later the bees stop feeding royal jelly to the young worker or drone larvae and change the diet to brood food. This consists of diluted honey or nectar and pollen. Young chosen queen larvae will continue with their diet of royal jelly until they born.
As the larva moves to the pupa stage, a brown wax cap is placed on the cell and metamorphous takes place, the same process that transforms a caterpillar into a butterfly. The larva will spin a cocoon around itself and has properties similar to silk. Listen to the audio. At the end of the period, the bee emerges by chewing through the brown wax cap unaided.
The photo shows eggs, larvae and a single pupa (hidden beneath the brown cap) of worker bees. The eggs are small and easily missed by the beekeeper. The tiny larvae, 3rd row, 2nd cell from the right is floating in a pool of royal jelly. An unhatched egg is diagonally above.