1. Age 18-35

2. BMI \<30 kg/m2

3. Premenopausal with regular cycles or currently taking an OC

4. Not currently or recently pregnant or nursing (within previous 6 months)

5. Non-smoker

6. No use of antibiotics within the prior 4 weeks

7. Competent to provide written informed consent (as judged by study team)

8. Willing to adhere to the OC regimen

9. Willingness to refrain from the use of aspirin or NSAIDS 10 days pior to the biopsy appointment and one week following the biopsy procedure

10. Willing and able to refrain from use of fish oils 10 days prior to the biopsy appointment and one week following the biopsy procedure

Oral Contraceptive (OC) Estrogen Dose and Breast Proliferation