Figuring out how to power cameras and other gadgets in Europe can seem tricky, but it’s easy enough once you know how.
The trick is to look for a sticker on the power adapter or plug that tells you the input voltage. The magic words to look for are something like this: "100-240V AC 50/60Hz". 100-240 tells you the voltage range: Europe standardized on 220 volts for its standard household power supply. So the voltage range on your device needs to cover 220 volts or more for your electronics to work in Italy, France and most of Europe. If your gadget can cope with a higher range, that's OK too (e.g. "90-240"). In all of these cases, you just need a simple (and cheap) plug adapter and the device itself will automatically adapt to the higher voltage.
Here's a video that shows you the various plug adapters and how they work:
Almost all of today's small electronics like cameras, mobile phones, laptops and chargers automatically adapt and you just need a plug adapter.
Devices that use more power, like hairdryers or portable kettles, almost always only work on US 110 volts. Check the label: if it says something like "120VAC" or a smaller range such as "100-130V" then you cannot use it in Europe without a voltage transformer. This is extremely important: if you plug a standard 120V hair dryer into 220V using a plug adapter, it will immediately burn out the dryer and may cause a fire.
The good news is that there are travel hairdryers etc. available that are designed to adapt to the voltage. But in general it is much harder to design a high power device that is adaptable to 110V and 220V, because to do so you need a very heavy and large voltage transformer.
External voltage transformers are available: they are rated by the amount of power they can supply, in Watts. So it might say on your electric kettle "1000W" -- that means you need a transformer rated for 1000W or greater. Again, it can be dangerous to exceed the maximum rating of a transformer: it will eventually melt and may catch fire. The more transformer a converter can supply, the larger and heavier it will be, so beware of smaller adapters if you need a lot of power.
The simple approach? Take devices that don't need voltage conversion. The good news is that these days, most of them don't. Take a travel hair dryer rather than lugging around a high current transformer: it's much lighter. Simply don't take portable kettles and other high power devices.