Why are breasts different sizes?

During puberty, breasts don't always receive identical amounts of the hormone that makes them grow. Why does this happen, and how common is perfect symmetry anyway?

How to choose the right bra cup size! For big breasts, and small

Breast Shapes: Understanding the Different Types

Breast Asymmetry: Causes and Diagnosis

Breast Asymmetry: 9 Reasons You Have Uneven Breasts - HealthyWomen

Women's Health

The infuriating truth about bra fittings revealed

My breasts are different sizes – how do i find the right bra?

Is It Normal to Have Different-Sized Breasts? - GoodRx

8 Types of Boobs in the World - Different Breast Sizes and Shapes

Study Finds: The Truth About Breast Lift & Cup Size - Dr. Izaddoost

Is It Normal to Have Different-Sized Breasts? - GoodRx

Breast Asymmetry: Causes and Diagnosis