Penis. PENIS! Got your attention? Keep it at attention - smoking can cause erectile dysfunction in men as young as 20.
"The Health Consequences of Smoking—50 Years of Progress. A Report of the Surgeon General." U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health. 2014. Report.http://www.surgeongeneral.gov/library/reports/50-years-of-progress/full-report.pdf