Sources | Medically Reviewed on 11/19/2019 Reviewed by Arefa Cassoobhoy, MD, MPH on November 19, 2019

IMAGES PROVIDED BY:

(1) Jose Luis Pelaez / Blend Images

(2) SuluImages / Workbook Stock

(3) Andrew Bret Wallis / Photodisc

(4) Fuse

(5) Gary John Norman / Digital Vision

(6) Nisian Hughes / The Image Bank

(7) Don Mason / Blend Images

(8) Andrew Bret Wallis / The Image Bank

(9) Monkey Business Images

(10) Frank Siteman / Science Faction

(11) Tina Stallard / The Image Bank

(12) Jonnie Miles / Photographer's Choice

(13) Image Source

(14) bilderlounge / beyond fotomedia

REFERENCES: