The purpose of this research study is to gain a better understanding of the changes that may occur in the breast when a woman uses an oral contraceptive (birth control pill). Some research indicates that women who use birth control pills with lower amounts of estrogen (a hormone in the birth control pill) may have lower breast cell growth than women who use birth control pills with a higher amount of estrogen; this research will examine that in detail.

Inclusion Criteria:

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

Exclusion Criteria:

1. Diabetes
2. Abnormal breast examination
3. Abnormal PT/INR and/or CBC with platelets test results (as determined by one of the study physicians)
4. History or current therapeutic or prophylactic use of anticoagulants
5. Known bleeding disorder or history of unexplained bleeding or bruising
6. History of breast cancer or previous diagnostic breast biopsy
7. Known allergy to local anesthetic