This document provides an overview of non-fungible tokens (NFTs), including their history from colored coins in 2012 to recent growth in 2021. Key concepts covered include the differences between fungible and non-fungible assets, common NFT use cases like art and collectibles, and technical standards like ERC-721 and ERC-1155. The document demonstrates how to create, mint, and list an NFT for sale using OpenSea and the Ethereum blockchain.

1. NON-FUNGIBLE
TOKENS. FROM SMART
CONTRACT CODE TO
MARKETPLACE
NFT Contracts, Presentation Part Ⅱ
11/4/2021

2. DISCLAIMER
§ The views and opinions expressed by the Presenter are those of the Presenter.
§ Presentation is not intended as legal or financial advice and may not be used as legal or
financial advice.
§ Every effort has been made to assure this information is up-to-date as of the date of
publication.

3. FUNGIBLE VS NON-FUNGIBLE
ASSETS
Fungible Non-fungible

4. BUZZ AND REALITY
What we read in news
Celebrities, Billionaires, Athletes
purchasing NFTs
… NFT was sold on … for $.....
What’s going on
One form of smart contracts,
ERC-721 has interesting
characteristics:
Can verifiably prove ownership
Ownership of NFTs can grant
some privileges within online
communities

5. DEFINITION
“A non-fungible token (NFT) is a unique
and non-interchangeable unit of data stored
on a digital ledger (blockchain). NFTs can be
used to represent easily-reproducible items
such as photos, videos, audio, and other
types of digital files as unique items, and use
blockchain technology to establish a verified
and public proof of ownership.”

6. “NFT” NAME ORIGIN
“NFT” was satisfactory to nearly everyone surveyed and is widely
applicable to a broad universe of distinguishable digital assets. We
recognize that “deed” is very descriptive for certain applications of
this standard (notably, physical property).
Alternatives considered: distinguishable asset, title,
token, asset, equity, ticket

7. HISTORY 2012 to 2021

8. HISTORY: COLORED COINS. 2012
Field Description Size
OAP Marker
A tag indicating that this
transaction is an Open
Assets transaction. It is
always 0x4f41.
2 bytes
Version number
The major revision
number of the Open
Assets Protocol. For this
version, it is 1 (0x0100).
2 bytes
Asset quantity count
A var-
integer representing the
number of items in
the asset quantity
list field.
1-9 bytes
Asset quantity list
A list of zero or
more LEB128-
encoded unsigned
integers representing
the asset quantity of
every output in order
(excluding the marker
output).
Variable
Metadata length
The var-integer encoded
length of
the metadata field.
1-9 bytes
OP_RETURN

9. HISTORY: PEPE MEMS. 2017
March 2017 — Rare Pepes on Ethereum -
Peperium “decentralized meme marketplace
and trading card game (TCG) that allowed
anyone to create memes that live eternally on
IPFS and Ethereum.”

10. HISTORY: CRYPTO KITTIES. 2017

11. 2020: FIRST IMMERSIVE CRYPTOART
FESTIVAL

12. 2021

13. COMMON USE CASES
Art/Collectables Games Luxury brands
Event and other
tickets
Sports
Athletic and
other
memorabilia
Supply chain
and logistics
Real estate
Proof of
ownership
Licenses and
certificates
Domain name
records

14. DAPP RADAR - NFT SALES IN REAL
TIME

15. NFT EXPERIENCE WITH
OPENSEA
Creating and selling token
on OpenSea as 1-2-3

16. 1. CREATING COLLECTION

17. 2. CREATING ITEM

18. 3. PUT ON SALE

19. WEEKLY NFT TRANSACTIONS
https://www.theblockcrypto.com/data/nft-non-fungible-tokens/nft-overview

20. WEEKLY NFT SALES
https://www.theblockcrypto.com/data/nft-non-fungible-tokens/nft-

21. AVERAGE PRICE FOR NFT
https://www.theblockcrypto.com/data/nft-non-fungible-tokens/nft-overview

22. NON-FUNGIBLE TOKEN
TRACKER
How to find popular NFT
projects on Ethereum
Mainnet?

23. NON-FUNGIBLE TOKEN TRACKER

24. EVOSNAILS

25. EVOSNAILS ON OPENSEA

26. DEEP DIVE NFT Contracts

27. COMMON TOKEN STANDARDS
ERC-721
Default
Gold Standard
Most widely used
Not suitable for minting NFTs in
mass
Transferring one token at a time
Contains “symbol” and “name”
ERC-1155
Dual purpose: fungible and non
fungible
Used often to tokenize things
like common gaming skins and
other commoditized items
Single contract to make various
types of NFT
Less information in blockchain
logs (in events)
All metadata in URI

28. ERC-721 USE CASES 1/3
ERC-721 token
How Many Tokens do I have?
Am I the owner?
function balanceOf(address _owner) external view returns (uint256);
function ownerOf(uint256 _tokenId) external view returns (address);
Anyon
e

29. ERC-721 USE CASES 2/3
ERC-721 token
Transfer to someone else (safe)
Transfer to someone else
(unsafe)
Owner
function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;
function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;
function transferFrom(address _from, address _to, uint256 _tokenId) external payable;
Owner New
Owner

30. ERC-721 USE CASES 3/3
ERC-721 token
Delegate
Owner
function approve(address _approved, uint256 _tokenId) external payable;
Operator
function setApprovalForAll(address _operator, bool _approved) external;
Is delegated to someone?
function getApproved(uint256 _tokenId) external view returns (address);
function isApprovedForAll(address _owner, address _operator) external view returns (bool);

31. ERC-721 FUNCTIONS
balanceOf(owner)
ownerOf(tokenId)
safeTransferFrom(from, to, tokenId)
transferFrom(from, to, tokenId)
approve(to, tokenId)
getApproved(tokenId)
setApprovalForAll(operator, _approved)

32. ERC-721 METADATA EXTENSION
name()
symbol()
tokenURI(uint256_tokenId)
{
"title": "Asset Metadata",
"type": "object",
"properties": {
"name": {
"type": "string",
"description": "Identifies the asset to which
this NFT represents"
},
"description": {
"type": "string",
"description": "Describes the asset to which
this NFT represents"
},
"image": {
"type": "string",
"description": "A URI pointing to a resource
with mime type image/* representing the asset to
which this NFT represents. Consider making any
images at a width between 320 and 1080 pixels and
aspect ratio between 1.91:1 and 4:5 inclusive."
}
}
}

33. ERC-721 ENUMERATION
EXTENSION
totalSupply()
tokenByIndex(uint256_index)
tokenOfOwnerByIndex(address_owner,uint256_index)

34. ERC-721 EVENTS
•Transfer(from, to, tokenId)
•Approval(owner, approved, tokenId)
•ApprovalForAll(owner, operator, approved)

35. DEMO Creating contract
Minting and Selling NFT

36. HANDS-ON EXERSICE ERC-721
FROM “SCRATCH”
Create
ERC-721
Compile Deploy
Check in
Explorer

37. OPEN ZEPPELIN CONTRACTS
WIZARD

38. URI WITH NAME, DESCRIPTION,
AND IMAGE
{
name: "Thor's hammer",
description: "Mj�lnir, the legendary hammer
of the Norse god of thunder.",
image: "https://cdn.pixabay.com/photo/2013/07
/12/12/58/tv-test-pattern-
146649_960_720.png",
strength: 20
}

39. REMIX

40. DEPLOY 721CONTRACT

41. MINT THE TOKEN

42. CHECK THE CONTRACT ON
ETHERSCAN

43. CHECK EVENTS ON ETHERSCAN

44. ADD TO OPENSEA

45. PUT TOKEN FOR SALE ON
OPENSEA

46. QUESTIONS?

47. STAY IN TOUCH
Gene Leybzon https://www.linkedin.com/in/leybzon/
https://www.meetup.com/members/90744
20/
https://www.leybzon.com