A non-fungible token (NFT) is a digital token that is built to represent any <a href="https://www.cryptoknowmics.com/news/nfts-and-digital-collectibles-selling-for-thousands-of-dollars-celebrities-cashing-in/">unique asset as a crypto resource</a>. NFT can be used to prove the ownership of physical goods like art, collectibles, a ticket to a concert or a sports event, real estate, or digital assets like digital artwork, domain name, or digital collectibles. In simple terms, you can consider it as a certificate of ownership for a virtual or physical asset. This certificate could further generate some value for you because of its rarity and authenticity.

The things that fall in the same category as songs could be represented as NFTs as each song has unique properties and needs to be identified as a separate asset. No two NFTs are interchangeable.

On the other hand, Fungible tokens are defined by the value they represent. Any two fungible tokens with the same value can be interchangeably used. For e.g., 1 DAI can be exchanged and used for any other 1 DAI, but 1 house represented as an NFT will not be equal to any other.

Metadata of NFT minting, ownership, and its entire history is saved as transactions in the blockchain. This is publicly verifiable and impossible to manipulate on the blockchain.

NFTs are <a href="https://www.cryptoknowmics.com/news/why-crypto-world-is-going-gaga-over-non-fungible-tokens/">secure just like</a> any fungible token such as Bitcoin, which means no one can steal them. Making a copy of an NFT would be the same as taking a photo of a painting or making a pirated copy of a movie, but there will only over be one original thing. Though actually, a copy of a digital work is literally as good as the original for just viewing, but that does not make it a part of the blockchain.

If an <a href="https://www.cryptoknowmics.com/news/why-ethereum-will-rise-in-2021/">NFT is created on Ethereum</a>, it is portable across many products and markets. Moreover, with the development of interoperability between different blockchains using protocols like Polkadot, NFT built on one blockchain could be used, traded, and sold on other blockchains as well without any intermediary.
<h2>NFTs on Ethereum</h2>
Most NFTs are issued and traded on Ethereum. The creation and lifecycle of an NFT are maintained by the smart contract. It can contain other logic such as giving royalty to the creator of an NFT any time the <a href="https://www.cryptoknowmics.com/news/nft-project-altcoins-hits-new-all-time-highs/">token</a> is further sold. 

Ethereum has developed some token standards to ensure tokens’ compatibility with existing decentralized exchanges. Most NFTs are built using the standard token interface called ERC-721. All NFTs built using this template have a tokenId. For each NFT, the pair of the address of the smart contract and the tokenId must be globally unique. The template provides the following functionalities to track and transfer NFTs:
<ul>
 	<li style="font-weight: 400">balanceOf: get the current token balance of an account.</li>
 	<li style="font-weight: 400">ownerOf: get the owner of a token.</li>
 	<li style="font-weight: 400">safeTransferFrom: transfers the ownership of an NFT from one address to another address</li>
 	<li style="font-weight: 400">approve: enable or disable approval for a third party or an operator to manage all NFTs of the owner.</li>
</ul>
Some NFT smart contracts implement other methods also other than the standard ones. According to <a href="https://etherscan.io/tokens-nft">Etherscan NFT tracker</a>, a total of 9,716 ERC-721 token contracts are deployed on the Ethereum main network till the time of writing.

Popular NFTs built on Ethereum according to their transaction volume are:
<ul>
 	<li style="font-weight: 400">Sorare: It is a global <a href="https://www.cryptoknowmics.com/news/top-four-decentralized-nft-applications-driving-10-million-volume-dappradar/">fantasy football game</a>. Users can collect limited-edition collectibles, make teams, manage their teams, and compete with other users.</li>
 	<li style="font-weight: 400">Unstoppable Domains: It builds domains on the blockchain which replace cryptocurrency addresses with human-readable names.</li>
 	<li style="font-weight: 400">Ethereum Name Service: It also offers simple and human-readable domain names to address resources both on and off the blockchain.</li>
 	<li style="font-weight: 400">CryptoKitties: Created by Dapper labs, it is a game centered around breedable, collectible digital creatures (virtual) called CryptoKitties. A digital cat was bought in 2018 for 600ETH which was worth $172,000 then.</li>
 	<li style="font-weight: 400">Gods Unchained Cards: It is a digital trading card game where you can trade cards you purchase or earn.</li>
</ul>
Some of the popular NFT marketplaces are:
<ul>
 	<li style="font-weight: 400">Terra Virtua: It is the first immersive digital collectibles platform. Users can choose digital merchandise from some big names in the entertainment industry. It also brings interactability to the users’ collectibles.</li>
 	<li style="font-weight: 400">SuperRare: It is a marketplace to collect and trade unique, single-edition digital artworks.</li>
</ul>
<h2>Other NFT Token Standards</h2>
For semi-fungible tokens, the token template ERC-1155 is used. It is a standard interface that manages multiple token types. ERC-721 token standard requires a separate contract to be deployed for each token type or collection. Ex. There are over 1lac different items in the game of World of Warcraft. If ERC-721 is used, each item type requires deploying a separate contract on the blockchain. This would place a lot of redundant smart contracts on the blockchain.

Using ERC-1155, different item types can now be stored in a single contract with the minimum possible amount of data needed to distinguish each token from the other. It implements methods to transfer single or batches of tokens between users.

Another improvement in the way NFTs are minted is proposed as EIP-2309. It is proposed to extend the capability of the ERC-721 token to support the creation and transfer of many tokens at one time.
<h2>Popular Uses of NFTs</h2>
Game developers develop NFTs for creating tradable in-game items. They can be traded on any decentralized platform. <a href="https://www.cryptoknowmics.com/news/nft-game-aavegotchi-will-launch-mainnet-in-early-january/">Aavegotchi</a> is one such project which combined NFTs with the realm of DeFi. It is a game offering digital collectibles backed by <a href="https://www.cryptoknowmics.com/news/everipedia-announces-aaves-investment-in-aavegotchi-nft-game/">Aave</a> interest-bearing aTokens. This offers new alternatives for yield farming. The collateralized aTokens increases the liquidity of the Aave lending pool which generates yield over time. In mid-2020, fans bought 1,25,000 NFT trading cards featuring Star Trek’s William Shatner.

NFT is gaining popularity because of its adoption by artists and growing interest in collectors. According to <a href="https://cryptoart.io/data" target="_blank" rel="nofollow noopener">Cryptoart data</a>, a total of 1,44,950 artworks are sold till now worth 2,34,890 ETHs ($405M). You can check out some popular NFT art galleries like Nifty Gateway, SuperRare, Foundation, MakersPlace, KnownOrigin, and Async Art.

Though it all seems like hysteria, the most expensive artworks sold till now are:
<ul>
 	<li style="font-weight: 400">Everydays: The First 5000 Days - created by Mike Winkelmann, professionally known as Beeple. This is a collage of 5000 images he created for his “Everyday” series. It is <a href="https://twitter.com/ChristiesInc/status/1370027970560106497" target="_blank" rel="nofollow noopener">sold</a> for 40,196 ETHs ($60M).</li>
 	<li style="font-weight: 400">Crossroad - Another artwork created by Beeple, under the project “The First Drop.” It is sold for 3,825 ETHs ($6.6M).</li>
</ul>
Recently, Twitter co-founder listed his <a href="https://www.cryptoknowmics.com/news/nft-of-first-tweet-sold-for-29-million-jack-dorsey-proceed-for-charity/">first-ever tweet for sale</a> as an NFT. It was sold at a whopping amount of $2.9M. However, the Tweet will remain publicly available on the platform even after the auction. The buyer would receive an NFT claiming that he is now the owner.

https://twitter.com/jack/status/20

Nike is trying to combine NFTs with real-world assets. It has attached NFTs with their sneakers series called CryptoKicks. Each pair of sneakers would be saved on the blockchain as an NFT. Further, this will be used to track the ownership and verify the authenticity of sneakers using blockchain.
<h2>Disadvantages</h2>
Development on blockchains is associated with a huge carbon footprint just like cryptocurrencies, but Ethereum is evolving to become energy-efficient. 

Many think NFTs to be of no physical value and no sense as it is not tangible. It sounds crazy to spend thousands of dollars buying digital tokens. However, many think it to be a bubble that will soon burst.
<h2>Conclusion</h2>
Many blockchain researchers believe that the destiny of NFTs lies somewhere else. However, we are every day seeing some meaningful applications of these digital tokens. In the future, NFTs could be combined with DeFi or may be traded on DEXs by any other crypto token. We believe that the main potential lies in using it for sectors like supply chain, real estate, digital identities, and we will see those uses sooner than later.

Evolution and Trends in Non-Fungible Tokens (NFTs)

Along with DeFi, the latest craze in the crypto world is of NFTs. People are creating digital assets of collectibles, art, in-game items among others.

Anubha is a keen follower of the manifold applications of blockchain technology. She is a doctoral candidate researching privacy constraints of the blockchain and is working to enhance user privacy in cryptocurrencies. She is a strong supporter of the vision of user-owned internet and believes blockchain as the key to it.

Evolution and Trends in Non-Fungible Tokens (NFTs)

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