Chapter 1 provides background information on e-cigarettes. Tobacco use among youth and young adults in any form, including e-cigarettes, is not safe. In recent years, e-cigarette use by youth and young adults has increased at an alarming rate. E-cigarettes are now the most commonly used tobacco product among youth in the United States. Chapter 2 highlights the rapidly changing patterns of e-cigarette use among youth and young adults, assesses what we know about the health effects of using these products, and describes strategies that tobacco companies use to recruit our nation's youth and young adults to try and continue using e-cigarettes. It also outlines interventions that can be adopted to minimize the harm these products cause to our nation's youth. Over the last decade, use of electronic cigarettes, known as e-cigarettes, in the United States has grown rapidly as use of traditional cigarettes declined among both adolescents and adults. Most e-cigarettes sold in the United States were thought to be imported, but e-cigarette import volume and tariff revenue were unknown because the Harmonized Tariff Schedule of the United States (HTS) did not contain separate statistical reporting numbers. New statistical reporting numbers went into effect on January 1, 2016. Chapter 3 reports on e-cigarettes imported into the United States in 2016. While chapter 4 reports on e-cigarettes imported into the United States from 2016 through 2018. E-cigarettes are battery-powered devices which simulate tobacco smoking by producing a heated vapor that resembles smoke. A number of explosions and fires have been attributed to e-cigarettes, causing some concern within the fire service community as discussed in chapter 5. Electronic cigarettes, known as "personal vaporizers" (PV) have experienced a significant increase in popularity for those seeking an alternative to smoking traditional tobacco products. The use of the e-cigarettes as an illicit drug delivery device is touted on websites, forums, blogs, and videos describing how best to use them for specific illicit drugs such as tetrahydrocannabinol, methamphetamine, fentanyl, and heroin as reported in chapter 6. Chapters 7 and 8 report on the 2019 outbreak of lung injury associated with e-cigarette use.