"E-cigarettes are 95% less harmful than tobacco and could be prescribed on the NHS in future to help smokers quit," BBC News reports.
This is the main finding of an evidence review (PDF, 485kb) carried out by Public Health England, a government agency that aims to protect and improve the nation's health and wellbeing, and reduce health inequalities.
Most e-cigarettes contain a battery, an atomiser and a replaceable cartridge. The cartridge contains nicotine in a solution of either propylene glycol or glycerine and water, and sometimes flavourings.
When you suck on the device, a sensor detects the air flow and starts a process to heat the liquid inside the cartridge, so it evaporates to form water vapour. Inhaling this vapour delivers a hit of nicotine straight to your lungs.