The resources of the body are primarily directed towards achieving overall growth during the initial stages of development. As the rate of general body growth slows down, resources are then redirected towards the maturation of reproductive tissues.

Sexual maturation occurs during adolescence because, during this period, the body shifts its focus from rapid overall growth to the maturation of specialized tissues, particularly those related to reproduction.

Individual differences in the timing and pace of puberty-related changes contribute to unique patterns of hair growth, breast or penis size, and overall sexual maturation among people, similar to variations in other physical features like nose or finger shapes.

The changes during puberty take place slowly over months and years. For example, facial hair growth in boys starts with a few scattered hairs and gradually becomes more uniform.

These changes do not occur at the same time or at a specific age for everyone. The onset and pace can vary widely among individuals.