Inclusion Criteria:
1. Women between 35 and 45 years old, both included
2. Participant with skin phototype III according to Fitzpatrick classification
3. Uniform skin color all over the four zones (difference in ITA° between the 4 zones should not be more than 4°)
4. Average ITA° (Individual Typologic Angle calculated value) on the back over the four zones between 28° and 41° at screening / inclusion visit
5. Absence of freckles, naevi, hypo or hyper pigmented regions, hairs, marks of tanning and tatoo on the investigational area on the lower back
6. Female of childbearing potential, who is not sexually active, or who is using an effective contraceptive method for at least one month before the beginning of the study, and throughout the study
7. Female participant of childbearing potential or pre-menopausal woman (with absence of menstruations for less than one year) willing to undergo urine pregnancy test
8. Participant with negative blood test results for Hepatitis B surface antigen (HBsAg), Hepatitis C antibodies (anti-HCV), and HIV, performed within 2 weeks prior to inclusion, with results documented in the participant's records.
9. Participant accepting to undergo 4 biopsies (3mm diameter punch) on the back
10. Participant willing and able to fulfill the study requirements and schedule
11. Participant informed about the study objectives and procedures, and able to understand them
12. Participant who has given written informed consent form
Exclusion Criteria:
1. Participant who is pregnant or who is planning to become pregnant during the study
2. Menopausal woman with absence of menstruation for more than one year
3. Participant having changed hormonal treatment (contraception...) within the last 3 months or having to planned to change during the study
4. Participant with bleeding disorders, bleeding with previous surgery and eventual use of drugs known to interfere with hemostasis which could impact on the biopsy collection
5. Participant with positive results on at least one of the following viruses: Hepatitis B or Hepatitis C or HIV test.
6. Any contra-indication for biopsies: medical history of allergy, hypersensitivity or any serious reaction to local anaesthesia, local antibiotic \& antiseptic, history of healing defects (hypertrophy, keloids…)
7. Having planned UV exposure of the investigational area (sunlight or sunbeds) throughout the study
8. Having used sunbeds or excessive sun exposure of the investigational area within the 3 months before inclusion
9. Having sunburn (erythema) on the back
10. Dermatological disorders affecting the investigational area (presence of naevi, freckles, excess hair or uneven skin tones, vitiligo, photo-dermatological problems)
11. History of skin cancer
12. History of abnormal response to sun
13. Presence of recent suntan (according to Investigator opinion) or photo-test marks
14. Any concomitant medical condition that may interfere with the study conduct in the opinion of the investigator
15. Having used within the month before inclusion any systemic medication for more than 5 consecutive days (e.g. steroidal and non-steroidal anti-inflammatory drugs, corticoids, insulin, antihistamines, antihypertensive, antibiotics -e.g. quinolone, tetracycline, thiazides, fluoroquinolones-)
16. Having used within the month before inclusion any medication known to cause abnormal responses to UV exposure (e.g. vitamin A derivatives, psoralen, aminolevulinic acid derivatives, etc.), or having planned to use these medications during the study
17. Having used within the 3 months before inclusion any depigmenting / whitening or pro-pigmenting topical treatments, or having planned to use these treatments during the study
18. Having used, within the past 6 months, any physical treatment including laser or phototherapy (PUVA, IPL, PDT…) on the investigational area, or having planned to use these treatments during the study
19. Having planned to perform intensive sport (\> 5 hours per week) or swim during the study
20. Participant who declares to be deprived of freedom by administrative or legal decision
21. Participant who cannot be contacted by telephone in case of emergency
22. Participant having participated within the 30 days before inclusion or currently participating in another clinical study
