Micro SIM vs. Nano SIM
SIM card is the primary component of a cell phone without which using the standard facilities such as calling and texting to other mobile phones is not possible. It is known as subscriber identity module and stores all the information of the user who is using the cell phone such as the mobile number, contacts, name, location and other lists such as calls and messaging logs. There are different versions of SIM cards that have been available over time. They differ in sizes and the amount of data that can be stored in them. A most initial form of these smart cards was known as standard SIM card, the later versions were known as mini cards which were smaller in size, and the next generation of these was known as micro while the latest versions are known as nano cards. There are only a few differences between the micro and nano versions, the main difference between them is, of course, the size, but there is no difference in the space provided. Micro is bigger in size while nano is smaller in size. Their sizes normally are different with a microcard having dimensions of 15×12×0.76 mm and nano with the size of 12.3×8.8×0.67 mm. Micro is known as 3FF, which is the third generation of these chips while nano is known as 4FF meaning the fourth generation of cellular chips. There are restrictions on the nano versions because they cannot be converted into micro, on the other hand, micro cards can be cut and made into nano cards efficiently which help a lot when the person wants to change their phone or moving towards new technology. Nano chips can be converted into micro with the aid of separate objects such as adapters. Most of the companies are moving towards nanotechnology now while micro technology could not last a longer time due to the rapid development taking place in the field of cellular networks. Another factor distinguishing between the two is that nanotechnology might last for even smaller time than micro because of the introduction of embedded cards. The thickness of micro cards was the same as small and original SIMs, but the thickness of nano-SIMS has been reduced which gives more space in the cell phone body for other features.

Key Differences
Micro cards are greater in size than the Nano
Micro cards have the same thickness as the original and mini-slots but in nano, the thickness was reduced for the first time.
To save nano card into micro, an adapter is required while no such tool is needed to turn vice versa.
Micro cards led to the origination of nano chips, while nano cards resulted in the making of embedded chips.
Both have different sizes but can store the same amount of memory among them.
The size of a micro card is 15×12×0.76 mm while nano comes with the size of 12.3×8.8×0.67 mm.
Micro card is known as 3FF while Nano card is known as 4FF.
Micro SIMS can be converted by hand into Nano SIMS, but nano cannot be turned into micro cards.
Comparison Chart
Specification
15 × 12 × 0.76 mm
12.3 × 8.8 × 0.67 mm
Interconversion
Micro SIMS can be converted by hand into Nano SIMS
Nano SIMS cannot be converted to Micro SIMS.
Chain
Micro cards led to the origination of Nano chips.
Nano cards resulted in the making of embedded chips.
Definition of Micro SIM
These cards for the phone are considered the third generation of chips which were employed in the mobile phones. Due to the bigger slots that were needed in the phone body, Apple decided to come up with another version of chips after the original and mini cards. There was a big difference from the previous versions, the length of the card was decreased almost 10 mm and brought from 25mm to 15mm, while the width was reduced from 15 mm to 12 mm, making it suitable for the newer mobile phones. The thickness was still the same because more thought was given to creating more space. This SIM card was first introduced in the iPhone 4 and was first utilized in the year 2010 although they were developed way back in 2003. Since the sizes of cell phones were being decreased so the need for such a chip which can give more room for advancement while providing the same space was made.
Definition of Nano SIM
With fast changes in the world of cell phone technology and new features being introduced within no time it was only a matter of time when an even smaller version of SIM cards was presented. There was a marked difference from the micro cards with the length of the card being decreased from 15 mm to 12.3 mm, there were changes in the width which lessened from 12 mm to 8.8 mm. For the first time, the thickness was also reduced from 0.76 mm to 0.67 mm, this was done to accommodate the iPhone 5 which was sleeker in design and required the depth along with other sizes to be reduced. There were many problems faced by people who wanted to upgrade their version from 4 to 5 because the slot sizes were changed. Therefore, the cards had to be cut to convert them into nano, currently though even more advanced versions of SIM cards are present in the market.