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Modulis 0 · Crypto basics
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Blockchains — why it matters and how to avoid costly mistakes

Video · 3 min.
Blockchains: separate worlds

Two grandmas at the market: one keeps a private notebook, the other writes on a public board. A blockchain is that board, so every record stays, and thousands of computers keep it. Each network is a separate country: SOL sent to an Ethereum address is lost. We also see Arbitrum and which protocol lives on which network.

Narrated, with light music
The full lesson with numbers and rules is below.
Watch on YouTube

What is a blockchain?

Blockchain — like separate countries

Imagine each blockchain is a separate country. Each country has its own currency, its own addresses, its own rules. You can't send Lithuanian euros straight to a Japanese bank — you have to convert them. In exactly the same way, you can't send SOL straight to an Ethereum address.

A blockchain is a network of computers that stores every transaction. Each network is a separate world.

Blokas #1genesisSandoriai: 4hash: a3fd9…prev: 0000…Blokas #2Sandoriai: 7hash: b3fe9…prev: a3fd9…Blokas #3Sandoriai: 10hash: c3ff9…prev: b3fe9…

Every block has its own "fingerprint" (hash) and references the hash of the block before it. That's why changing an old transaction is impossible — it would break the entire chain after it.

The most important rule — and it's simple

Every blockchain is a separate network. SOL only exists on the Solana network, ETH only on the Ethereum network. That means there's just one thing you need to know: before sending, check the address. Starts with 0x = Ethereum, doesn't = Solana. Check that, and you know you're sending correctly.

The core networks in our strategy

Affiliate link

Some of the links in this lesson (Jupiter, Nexo, Deribit) are affiliate links. They cost you nothing extra, but the platform pays a commission. That helps keep the school free. Prefer not to use them? Just type the address by hand.

Solana SOL

What mattersSolana
Address formatLetters and numbers, e.g. 7Xm...kP9
Transaction speed1–2 seconds
Transaction costUnder $0.01
"Gas" currencySOL
DeFi protocolsKamino, Orca, Meteora, Jupiter
WalletJupiter Walletad (recommended)

Solana is the fastest and cheapest network in our strategy. Every operation costs a fraction of a cent. Ideal for active DeFi use.

Ethereum ETH

What mattersEthereum
Address formatStarts with 0x..., e.g. 0xAb5...3F7
Transaction speed~12 seconds
Transaction cost~$0.01–0.30 (mainnet)
"Gas" currencyETH
DeFi protocolsAave, Uniswap
WalletMetaMask

Ethereum is the oldest and largest DeFi network. It has the most money and the most protocols. Fees are low during quiet periods, but they move with network load — during peak times they can temporarily jump several times over, so before a larger operation it's worth checking etherscan.io/gastracker.

Arbitrum (Ethereum Layer 2) ETH

What mattersArbitrum
Address formatSame as Ethereum: 0x...
Transaction speed<1 second
Transaction cost<$0.01–0.05
"Gas" currencyETH
DeFi protocolsAave, Uniswap, Camelot
WalletMetaMask (need to add the Arbitrum network)
Arbitrum — a highway alongside Ethereum

Ethereum mainnet is usually free-flowing and cheap, but during a jam the fee jumps several times over. Arbitrum is like a highway running alongside it — the fee stays small and stable (under $0.01) even during a jam, and the security is the same (because it inherits Ethereum's protection).

In our strategies we always use Arbitrum instead of Ethereum mainnet. Faster and more predictable.

Comparing the networks

SolanaEthereumArbitrum
Speed1–2 sec~12 sec<1 sec
CostUnder $0.01~$0.01–0.30<$0.01–0.05
SecurityHighHighestEthereum-level
DeFi protocolsKamino, Orca, MeteoraAave, UniswapAave, Uniswap
WalletJupiter WalletMetaMaskMetaMask

How to transfer money

Within the same network (simple)

A transfer within the same network is simple. Like a payment within the same bank:

Between different networks — there's a safe path

Moving assets from one network to another is possible — it just matters which path you take. Direct transfers use bridges (digital connectors between networks), but there's a simpler and safer alternative, which I'll show below.

Why we choose an exchange, not a bridge

Bridges have historically been the most common point of major losses in DeFi — a few well-known cases:

And this isn't history: in 2026 roughly $340M was stolen from bridges across 14 incidents — bridges are still the single most expensive risk category in DeFi.

The solution is simple: between Solana and Ethereum, travel through a CEX exchange (shown below). That way you simply avoid this whole risk point — not out of fear, but by choosing a better path.

How to transfer between networks correctly

The safest path: through a CEX exchange

Instead of a risky bridge, use an exchange as the intermediary. It takes longer, but it's safer.

Solana → Ethereum:

  1. Jupiter Wallet → send SOL to Nexo (via the Solana network)
  2. Nexo: sell SOL → buy ETH
  3. Nexo → withdraw ETH to MetaMask (via the Arbitrum network!)

Ethereum → Solana:

  1. MetaMask → send ETH to Nexo
  2. Nexo: sell ETH → buy SOL
  3. Nexo → withdraw SOL to Jupiter Wallet (via the Solana network)
Why through an exchange?

Even though it looks longer, this path is the safest because:

If you still want a bridge

If you need a bridge for Ethereum → Arbitrum (the same network type, lower risk):

Between Solana and Ethereum: don't use a bridge. Use the exchange path.

5 spots you're now learning to check

These five situations cause the most confusion for beginners. The good news — each one has a clear check that, once done, lets you move on calmly:

#MistakeWhat happensHow to avoid it
1SOL sent to an Ethereum addressMoney lost foreverCheck the address format: 0x... = ETH, otherwise = SOL
2ETH withdrawn on Ethereum mainnet when you needed ArbitrumExtra step — you'll need to move it to Arbitrum again (bridge or via an exchange)Pick the "Arbitrum" network on the exchange
3USDC (a stable-value cryptocurrency pegged to $1) sent on the wrong networkMoney lost or stuckUSDC exists on multiple networks — always check!
4Bridge program hackedAll funds in the bridge lostDon't use bridges — use an exchange
5Forgot to add the Arbitrum network to MetaMaskWon't accept the transferchainlist.org → "Arbitrum One" → Add

USDC — one currency, but several networks

USDC on multiple networks — good to know upfront

USDC isn't a single token. It exists separately on multiple networks:

They aren't directly interchangeable — Solana USDC can't be sent straight to an Ethereum address. The solution is simple: if you need USDC on another network, you go through an exchange as the intermediary.

It's like euros in different banks — the currency is the same, but the transfer goes through an intermediary. Once you understand this, moving USDC between networks becomes just another operation you know how to do.

Network-selection checklist

Before every transfer, check:

  1. Do I know which network I'm sending to? (Solana / Ethereum / Arbitrum)
  2. Is the recipient's address valid for this network? (0x... = ETH/Arbitrum, otherwise = Solana)
  3. Does the exchange/wallet support this network? (check the withdraw options)
  4. Do I have "gas" on that network? (SOL on Solana, ETH on Ethereum/Arbitrum)
  5. Is this my first time? → always test with a small amount!

Map of protocols and networks

ProtocolNetworkWalletLink
KaminoSolana SOLJupiter Walletkamino.finance
OrcaSolana SOLJupiter Walletorca.so
MeteoraSolana SOLJupiter Walletmeteora.ag
JupiterSolana SOLJupiter Walletjup.agad
AaveEthereum/Arbitrum ETHMetaMaskapp.aave.com
UniswapEthereum/Arbitrum ETHMetaMaskapp.uniswap.org
DeribitadCentralized exchange—deribit.comad

Remember: Orca and Meteora = Solana only. Uniswap = Ethereum/Arbitrum only. Never mix networks.

Quick check
What happens if you send SOL to an Ethereum address?
Practice task
0 / 5
Learn to tell networks apart from an address

The most expensive crypto mistake is mixing up networks. This task will teach you to recognize a network from its address format in about 5 minutes — no purchase needed.

This is learning, not investing — use only small amounts you treat as tuition.

You just learned to tell networks apart and choose a safe path between them — this is the foundation the rest of the strategy stands on. Most people never fully piece this together.

Ethereum vs SolanaStablecoins
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Solana address

CUj6wYQLSBxidzm7Lqtkxbw2d8Sv2H2tbJELyAjR756M

Solana network only

Send SOL or SPL tokens (e.g. USDC) only on the Solana network. Sending from an exchange over a different network loses the funds permanently — nobody can recover them.

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