The Human egg is very small and grows within a small tiny cyst called follicle.
Each month at the beginning of the cycle one follicle grows from a size of 5 mm to a mature size of 20 mm on day 13-14 of the cycle when it ruptures to release its egg. It is now possible to follow up the growth of the follicle by ultrasound i.e follicle tracking and release the egg 36-40 hour latte by means of an injection ( HCG) .
Follicle tracking is usually carried out in assisted conception cycles inorder to time intercourse or in conjunction with artificial insemination.