Health awareness days come and go, as do fashions...but are e-cigarettes a worthy fad? With awareness growing, the debate around e-cigarettes is also heating up. How much of an alternative are e-cigarettes to traditional cigarettes? And how should they be treated by the law?

E-cigarettes consist of a vaporizer and a container with a flavored nicotine solution. When the smoker draws on the e-cigarette, the liquid vaporizes and the vapor can be inhaled. The device is battery-powered, and the battery has to be recharged regularly, for example via a USB-connector on a computer.

The most popular solutions are tobacco and tobacco-menthol flavored. Then there are fruity flavors, such as strawberry and apple. You can choose between different nicotine strengths, but there are also solutions which do not contain any nicotine at all - or any flavor.

There are electronic cigars and pipes and a mini-version of a cigarette. A one-way cigarette for the occasional smoker costs about ten euros.

Smoking is defined as "breathing in smoke from burning substances, [or] burning parts of plants." The main difference with e-cigarettes is nothing burns. That's why e-cigarettes are said to be less harmful than tobacco smoking. But as the liquids contain nicotine, they can still cause a strong addiction.

There's a big debate over whether e-cigarettes should fall under smoking legislation - in Germany and other European countries. If they were treated the same way as normal cigarettes, e-cigarettes would have to be banned from restaurants and pubs. But for now they are - technically - allowed.

E-cigarette liquids contain many chemicals. One, for example, is propylene glycol, a colorless, almost odorless organic compound. It is used in smoke machines, as a solvent in many pharmaceuticals, as a food additive, and in toothpaste.

So is it better to continue smoking tobacco cigarettes or switch to e-cigarettes? Some experts say e-cigarettes are less harmful. But your best option is to stop smoking altogether. More and more studies are finding health risks associated with e-cigarettes. But there are no long-term studies yet. So who knows what we'll find down the track.

An international study found many of us believe only older people are at risk of heart attacks - and as a result, that only older people have to be careful. But the German Heart Foundation says that's not true. The earlier you start looking after your heart - through an active lifestyle and healthy diet - the better. After all, you've only got one heart!

The heart is a marvel of technology. The fist-sized, hollow muscle contracts about 70 times per minute, pumping up to 10,000 liters of blood through the body. And it does that your whole life. If necessary, the heart can pump about five times that much blood - for instance, when we are jogging.

The heart may be "just" a muscle - but it's a very special one. Like the muscles in your legs and arms, it can contract as fast and with as much power. But the heart has incredible stamina, and never gets tired. What's more, all heart muscle cells are linked, so they contract in unison.

If a heart beats slower than it should, a patient can be fitted with a pacemaker. First implanted in 1958, the device sends electrical impulses to the heart muscle. These days, pacemakers can function for from five to 12 years - on average, about eight.

To operate on a heart, surgeons have to stop it temporarily. This halts the circulation of blood - which would technically be fatal. But in the 1950s, scientists were able to solve this problem by developing the heart-lung machine. That machine takes over the function of the heart and lungs, enriching the blood with oxygen and pumping it through the body.

Modern medicine allows doctors to examine and perform surgery on the heart without cutting open the patient's ribcage. Instead, an intracardiac catheter - more or less a thin plastic tube - is inserted through veins and arteries in the groin, the elbow or the wrist. This tube is then pushed into the heart, requiring only local anesthesia.

If a heart valve is not working or worn out, you need a new one. Doctors might use a biological replacement from pigs, and mechanical heart valves made from metal are also an alternative. Modern artificial heart valves are foldable (pictured above) and can be inserted in endoscopic surgery via a catheter. This way, no open-heart operation is needed.

The first heart transplantation took place in 1967 - quite a sensation, back then. Nowadays, this operation is no longer a rarity. Every year, surgeons around the world transplant several thousand donor hearts from people who have died. The patients who receive a donor heart, however, have to take medication for the rest of their lives to prevent their own body from rejecting the foreign organ.

Donor hearts are rare, and there are waiting lists for recipients. If a heart is not working properly anymore, an artificial heart may support it. In that case, the sick heart stays in the body, and is supported by an implanted pump. This pump is powered by an external energy supply.

One research dream is to create an artifical heart that can replace the sick patient's heart completely. It would be inserted into the body, not require any external connection and would beat for many years without failure. Not an easy task - although some prototypes already exist.