diff --git a/UTXOPool.go b/UTXOPool.go
new file mode 100644
index 000000000..79073170a
--- /dev/null
+++ b/UTXOPool.go
@@ -0,0 +1,37 @@
+package main
+
+// UTXOPool is the data structure to store the current balance.
+type UTXOPool struct {
+	utxos map[string]int
+}
+
+// func (utxoPool *UTXOPool) handleTransaction(transaction Transaction, receiver string) {
+// 	if !isValidTransaction(transaction) {
+// 		return
+// 	}
+// 	// utxoPool[]
+// }
+
+// func (utxoPool *UTXOPool) isValidTransaction(transaction Transaction) {
+// 	const { inputPublicKey, amount, fee } = transaction
+// 	const utxo = this.utxos[inputPublicKey]
+// 	return utxo !== undefined && utxo.amount >= (amount + fee) && amount > 0
+// }
+
+// func (utxoPool *UTXOPool) handleTransaction(transaction, feeReceiver) {
+//     if (!this.isValidTransaction(transaction))
+//       return
+//     const inputUTXO = this.utxos[transaction.inputPublicKey];
+//     inputUTXO.amount -= transaction.amount
+//     inputUTXO.amount -= transaction.fee
+//     if (inputUTXO.amount === 0)
+//       delete this.utxos[transaction.inputPublicKey]
+//     this.addUTXO(transaction.outputPublicKey, transaction.amount)
+//     this.addUTXO(feeReceiver, transaction.fee)
+//   }
+
+//   func (utxoPool *UTXOPool) isValidTransaction(transaction Transaction) {
+//     const { inputPublicKey, amount, fee } = transaction
+//     const utxo = utxoPool.utxos[inputPublicKey]
+//     return utxo !== undefined && utxo.amount >= (amount + fee) && amount > 0
+//   }
diff --git a/block.go b/block.go
index dd0afd1ff..9af9cac92 100644
--- a/block.go
+++ b/block.go
@@ -10,28 +10,30 @@ import (
 // Block keeps block headers
 type Block struct {
 	Timestamp     int64
-	Data          []byte
+	utxoPool      []UTXOPool
 	PrevBlockHash []byte
 	Hash          []byte
 }
 
-// SetHash calculates and sets block hash
+//SetHash calculates and sets block hash
 func (b *Block) SetHash() {
 	timestamp := []byte(strconv.FormatInt(b.Timestamp, 10))
-	headers := bytes.Join([][]byte{b.PrevBlockHash, b.Data, timestamp}, []byte{})
+	// headers := bytes.Join([][]byte{b.PrevBlockHash, b.Data, timestamp}, []byte{})
+	headers := bytes.Join([][]byte{b.PrevBlockHash, timestamp}, []byte{})
 	hash := sha256.Sum256(headers)
 
 	b.Hash = hash[:]
 }
 
 // NewBlock creates and returns Block
-func NewBlock(data string, prevBlockHash []byte) *Block {
-	block := &Block{time.Now().Unix(), []byte(data), prevBlockHash, []byte{}}
+func NewBlock(utxoPool []UTXOPool, prevBlockHash []byte) *Block {
+
+	block := &Block{time.Now().Unix(), utxoPool, prevBlockHash, []byte{}}
 	block.SetHash()
 	return block
 }
 
 // NewGenesisBlock creates and returns genesis Block
 func NewGenesisBlock() *Block {
-	return NewBlock("Genesis Block", []byte{})
+	return NewBlock([]UTXOPool{}, []byte{})
 }
diff --git a/blockchain.go b/blockchain.go
index 7d72857b7..3662f6868 100644
--- a/blockchain.go
+++ b/blockchain.go
@@ -8,7 +8,9 @@ type Blockchain struct {
 // AddBlock saves provided data as a block in the blockchain
 func (bc *Blockchain) AddBlock(data string) {
 	prevBlock := bc.blocks[len(bc.blocks)-1]
-	newBlock := NewBlock(data, prevBlock.Hash)
+
+	// TODO(minhdoan): Parse data.
+	newBlock := NewBlock({}, prevBlock.Hash)
 	bc.blocks = append(bc.blocks, newBlock)
 }
 
diff --git a/transaction.go b/transaction.go
new file mode 100644
index 000000000..0e68efc2e
--- /dev/null
+++ b/transaction.go
@@ -0,0 +1,35 @@
+package main
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/gob"
+	"log"
+	"strings"
+)
+
+const subsidy = 10
+
+// Transaction represents a Bitcoin transaction
+type Transaction struct {
+	ID   []byte
+	data string
+}
+
+func (tx *Transaction) Parse() {
+	strings.Split("a,b,c", ",")
+}
+
+// SetID sets ID of a transaction
+func (tx *Transaction) SetID() {
+	var encoded bytes.Buffer
+	var hash [32]byte
+
+	enc := gob.NewEncoder(&encoded)
+	err := enc.Encode(tx)
+	if err != nil {
+		log.Panic(err)
+	}
+	hash = sha256.Sum256(encoded.Bytes())
+	tx.ID = hash[:]
+}
diff --git a/utils.go b/utils.go
index 8651f741c..e3813f87a 100644
--- a/utils.go
+++ b/utils.go
@@ -5,6 +5,8 @@ import (
 	"encoding/binary"
 	"encoding/gob"
 	"log"
+	"strconv"
+	"strings"
 )
 
 // IntToHex converts an int64 to a byte array
@@ -37,3 +39,32 @@ func DeserializeBlock(d []byte) *Block {
 
 	return &block
 }
+
+// Helper library to convert '1,2,3,4' into []int{1,2,3,4}.
+func ConvertIntoInts(data string) []int {
+	var res = []int{}
+	items := strings.Split(data, " ")
+	for _, value := range items {
+		intValue, err := strconv.Atoi(value)
+		checkError(err)
+		res = append(res, intValue)
+	}
+	return res
+}
+
+// Helper library to convert '1,2,3,4' into []int{1,2,3,4}.
+func ConvertIntoMap(data string) map[string]int {
+	var res = map[string]int
+	items := strings.Split(data, ",")
+	for _, value := range items {
+		pair := strings.Split(value, ":")
+		if len(pair) == 2 {
+			intValue, err := strconv.Atoi(pair[1])
+			if err != nil {
+				pair[0] = strings.Trim(pair[0])
+				res[pair[0]] = intValue
+			}
+		}
+	}
+	return res
+}
diff --git a/utils_test.go b/utils_test.go
new file mode 100644
index 000000000..bc7255297
--- /dev/null
+++ b/utils_test.go
@@ -0,0 +1,25 @@
+package main
+
+import "testing"
+
+func TestConvertIntoMap(t *testing.T) {
+	data := "minh:3,mike:2"
+	res := ConvertIntoMap(data)
+	if len(res) != 2 {
+		t.Errorf("Result should have 2 pairs (key, value)")
+	}
+	if val, ok := res["minh"]; !ok {
+		t.Errorf("Result should contain key minh")
+	} else {
+		if res["minh"] != 3 {
+			t.Errorf("Value of minh should be 3")
+		}
+	}
+	if val, ok := res["mike"]; !ok {
+		t.Errorf("Result should contain key mike")
+	} else {
+		if res["minh"] != 3 {
+			t.Errorf("Value of minh should be 2")
+		}
+	}
+}