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(Pocket-lint) - We live in a world obsessed with size. We like our gadgets small, our electronics compact and our mobile phones pocket-sized. Heck even our SIM cards need to be tiny, otherwise we put ourselves in danger of being subjected to SIM-size ridicule. 

Enter the micro-SIM, the modern day mobile phones answer the cappuccino; small and potent. Micro-SIMs are becoming a bit of a tech trend amongst top end smartphones, making appearances first in the iPhone 4 and now the iPad, iPhone 4S, Motorola RAZR and the Nokia Lumia 800. 

Thing is what exactly are they? What do they do? Most important of all, do you need one? 

What is a micro-SIM?

A Micro SIM is, at its most basic level, just the same as a standard SIM card, albeit smaller. But then what is a SIM card? Well, whenever you want to use a mobile phone you need some way of telling it which mobile network you are subscribed to. This is what the SIM card is for, storing network specific info that allows you to be identified by whatever mobile phone network you use. Without a SIM your phone simply wont work. There is all sorts of other hi-tech security related complexity stored on a SIM, as well as, if you have them, plentiful mobile phone contacts.

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In technology land, where everything exists in smaller than Lilliputian form, a normal SIM card is actually quite a big thing. Its size takes up a relatively large amount of internal space within a phone, stopping it being as thing as a designer would have hoped. Hence the need for a micro-SIM, which first made its appearance in the iPhone 4 and iPad, some of the thinnest gadgets out there. 

A bit of SIM nostalgia here for you; the thing we consider to be a conventional SIM, that is the ones we use in normal phones, is actually a smaller version of the credit card sized SIMs used in the old mobile bricks people carried in the 90s. The micro-SIM is more like a micro micro-SIM in reality. 

Do I need a micro-SIM? 

All but the latest smartphones and Apple devices don't require a micro-SIM to get themselves going. You can sit comfortably knowing that your network provider will have given you the right SIM to stick into your new handset. 

Say, for example, you buy an iPhone 4S, then expect a micro-SIM to come with it. A Galaxy S II? Yours should be a normal SIM. What happens, however, if you buy an unlocked device that needs a micro-SIM? Well then you are going to want to let your network provider know about it and get your number swapped over so you can start using your new device.

Those on O2 want to take a look here, Vodafone here, T-Mobile here, Orange here and finally Three needs a call on 333 to get things swapped over. 

Where did micro-SIMs come from? 

The idea of the micro-SIM comes from the European Telecommunications Standards Institute who invented the 12 x 15mm blighters to fit inside devices that were just too small to take a 15 x 25mm SIM card. 

The first time we saw a micro-SIM make an appearance in a piece of consumer technology was in the first generation iPad. Steve Jobs, always a fan of setting trends, announced the iPad would use the new SIM, leaving many wandering what exactly they were.

The micro-SIM is known to manufacturers as the 3FF or third form factor. As of now in the UK every major network operator supports the cards, partly due to the fact that every major operator supports the iPhone and iPad.

Can't I just cut my normal SIM into a micro-SIM? 

Well you can always try, but good luck getting things accurate enough for the newly trimmed SIM to sit inside your phone. We recommend this only for the most steady handed. If, however, you do make the decision to chop your big SIM down, here is a quick guide to doing it.

The first thing you are going to want is a ruler, to ensure you hit that 12 x 15mm size. You are then going to want something to score the measurements onto the plastic surface of the SIM holder. Once you have things marked up accurately then grab the scissors and get cutting. You want this to be straight as possible as if the SIM doesn't sit clean in its holder then it wont line up perfectly with the contacts in the phone. 

Get it right and you have just saved yourself a fair bit of hassle and in some cases expense, as networks can charge for a micro-SIM to be posted. 

Can I use a micro-SIM in a SIM slot?

Yes, but you will need a micro-SIM to SIM adapter, or otherwise known as a piece of plastic. You can get these from mobile phone shops if you smile nicely, or via the Internet if you're willing to pay a couple of quid plus postage. Once you get one, all you have to do is slip your micro-SIM card into the SIM adapter and then put the whole thing in your phone. 

Will more phones use micro-SIMs?

In all likelihood, given the amount of extra space a micro-SIM allows a phone, we expect to see plenty more handsets using them. The newly announced Motorola RAZR for example uses a micro-SIM. On top of that there is the new Nokia Lumia 800 and of course the iPhones and iPads. 

All in all it looks like more flagship phones are picking up micro-SIMs, meaning at some point you will probably have to switch to one, but at least now you should know what's what. 

Anything we missed on the micro-SIM? Let us know in the comments below...

Writing by Hunter Skipworth. Originally published on 16 April 2013.