Explore cutting-edge blockchain technologies and the future of Web3
Layer 2 (L2) solutions are built on top of Ethereum (Layer 1) to make transactions faster and cheaper while inheriting Ethereum's security.
Ethereum mainnet is like a highway with traffic. Layer 2 is like adding express lanes that handle most traffic off the main road, then periodically report back to the main highway.
Assume transactions are valid by default, only verify if challenged. Examples: Optimism, Arbitrum.
✅ Pros:
❌ Cons:
Use zero-knowledge proofs to verify transactions. Examples: zkSync, StarkNet, Polygon zkEVM.
✅ Pros:
❌ Cons:
Independent blockchains with their own consensus. Example: Polygon PoS.
✅ Pros:
❌ Cons:
Bridges allow you to move assets between different blockchains. Essential for a multi-chain future.
You lock tokens on Chain A, and equivalent tokens are minted on Chain B. When you bridge back, tokens on Chain B are burned and unlocked on Chain A.
Popular Bridges
Hop Protocol, Across, Stargate, Synapse
Use Cases
Move assets to cheaper chains, access different DeFi protocols
Bridges are frequent targets for hackers. Only use well-audited bridges and don't bridge more than you can afford to lose. Many major hacks have targeted bridges.
NFT marketplaces let users buy, sell, and trade non-fungible tokens. Understanding how they work is key to building NFT applications.
Minting
Creating new NFTs and storing metadata on IPFS
Listing
Sellers list NFTs for sale at fixed price or auction
Buying
Buyers purchase NFTs, smart contract handles transfer
Royalties
Creators earn percentage on secondary sales
// Simple NFT Marketplace Contract
contract NFTMarketplace {
struct Listing {
address seller;
uint256 price;
bool active;
}
mapping(address => mapping(uint256 => Listing)) public listings;
// List NFT for sale
function listNFT(address nftContract, uint256 tokenId, uint256 price) external {
IERC721(nftContract).transferFrom(msg.sender, address(this), tokenId);
listings[nftContract][tokenId] = Listing(msg.sender, price, true);
}
// Buy NFT
function buyNFT(address nftContract, uint256 tokenId) external payable {
Listing memory listing = listings[nftContract][tokenId];
require(listing.active, "Not for sale");
require(msg.value >= listing.price, "Insufficient payment");
// Transfer NFT to buyer
IERC721(nftContract).transferFrom(address(this), msg.sender, tokenId);
// Pay seller
payable(listing.seller).transfer(listing.price);
// Mark as sold
listings[nftContract][tokenId].active = false;
}
}DAOs (Decentralized Autonomous Organizations) are organizations governed by smart contracts and token holders, not traditional management.
A DAO is like a company where shareholders vote on every decision, and the votes are automatically executed by code. No CEO needed!
Governance Tokens
Hold tokens = voting power
Proposals
Members submit proposals for changes
Voting
Token holders vote on proposals
Execution
If passed, smart contract executes automatically
Blockchains can't access external data (weather, prices, sports scores). Oracles bridge this gap by feeding real-world data to smart contracts.
Smart contracts are isolated from the outside world. They can't make HTTP requests or access APIs. Oracles solve this by bringing external data on-chain in a decentralized way.
// Using Chainlink Price Feed
import "@chainlink/contracts/src/v0.8/interfaces/AggregatorV3Interface.sol";
contract PriceConsumer {
AggregatorV3Interface internal priceFeed;
constructor() {
// ETH/USD price feed on Ethereum mainnet
priceFeed = AggregatorV3Interface(
0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419
);
}
function getLatestPrice() public view returns (int) {
(
,
int price,
,
,
) = priceFeed.latestRoundData();
return price; // Returns price with 8 decimals
}
}Price Feeds
Real-time asset prices (ETH/USD, BTC/USD, etc.)
VRF (Verifiable Random Function)
Provably fair randomness for games and NFTs
Automation
Trigger functions based on conditions
While Ethereum dominates smart contracts, other blockchains offer different trade-offs and features.
Ultra-fast, low-cost transactions
Fast finality, subnet architecture
Internet of blockchains
Multi-chain architecture
Blockchain technology is rapidly evolving. Here are key trends shaping the future:
Smart contract wallets with better UX - social recovery, gas sponsorship, batch transactions
Privacy and scalability through ZK technology - private transactions, identity verification
Tokenizing real estate, bonds, commodities - bringing traditional finance on-chain
Decentralized AI models, on-chain ML, AI-powered smart contracts
Separating execution, settlement, and data availability - Celestia, EigenLayer
You've completed the Blockchain & Web3 course! You now have a solid foundation in blockchain technology, smart contracts, DeFi, and Web3 development. Keep building, keep learning, and welcome to the future of the internet!