diff --git a/object/environment.go b/object/environment.go
new file mode 100644
index 0000000..aed4862
--- /dev/null
+++ b/object/environment.go
@@ -0,0 +1,30 @@
+package object
+
+func NewEnvironment() *Environment {
+	s := make(map[string]Object)
+	return &Environment{store: s}
+}
+
+type Environment struct {
+	store map[string]Object
+	outer *Environment
+}
+
+func (e *Environment) Get(name string) (Object, bool) {
+	obj, ok := e.store[name]
+	if !ok && e.outer != nil {
+		obj, ok = e.outer.Get(name)
+	}
+	return obj, ok
+}
+
+func (e *Environment) Set(name string, val Object) Object {
+	e.store[name] = val
+	return val
+}
+
+func NewEnclosedEnvironment(outer *Environment) *Environment {
+	env := NewEnvironment()
+	env.outer = outer
+	return env
+}
diff --git a/object/object.go b/object/object.go
new file mode 100644
index 0000000..91806e6
--- /dev/null
+++ b/object/object.go
@@ -0,0 +1,181 @@
+package object
+
+import (
+	"bytes"
+	"fmt"
+	"hash/fnv"
+	"strings"
+
+	"github.com/0daryo/ody/ast"
+)
+
+const (
+	INTEGER_OBJ         = "INTEGER"
+	BOOLEAN_OBJ         = "BOOLEAN"
+	NULL_OBJ            = "NULL"
+	RETURN_VALUE_OBJECT = "RETURN_VALUE"
+	ERROR_OBJ           = "ERROR"
+	FUNCTION_OBJ        = "FUNCTION"
+	STRING_OBJ          = "STRING"
+	BUILTIN_OBJ         = "BUILTIN"
+	ARRAY_OBJ           = "ARRAY"
+	HASH_OBJ            = "HASH"
+)
+
+type HashPair struct {
+	Key   Object
+	Value Object
+}
+
+type Hash struct {
+	Pairs map[HashKey]HashPair
+}
+
+func (h *Hash) Type() ObjectType { return HASH_OBJ }
+func (h *Hash) Inspect() string {
+	var out bytes.Buffer
+
+	pairs := []string{}
+	for _, pair := range h.Pairs {
+		pairs = append(pairs, fmt.Sprintf("%s: %s", pair.Key.Inspect(), pair.Value.Inspect()))
+	}
+	out.WriteString("{")
+	out.WriteString(strings.Join(pairs, ", "))
+	out.WriteString("}")
+
+	return out.String()
+}
+
+type Array struct {
+	Elements []Object
+}
+
+func (ao *Array) Type() ObjectType { return ARRAY_OBJ }
+func (ao *Array) Inspect() string {
+	var out bytes.Buffer
+
+	elements := []string{}
+	for _, e := range ao.Elements {
+		elements = append(elements, e.Inspect())
+	}
+
+	out.WriteString("[")
+	out.WriteString(strings.Join(elements, ", "))
+	out.WriteString("]")
+
+	return out.String()
+}
+
+type BuiltinFunction func(args ...Object) Object
+
+type Builtin struct {
+	Fn BuiltinFunction
+}
+
+func (b *Builtin) Type() ObjectType { return BUILTIN_OBJ }
+func (b *Builtin) Inspect() string  { return "builtin function" }
+
+type String struct {
+	Value string
+}
+
+func (s *String) Type() ObjectType {
+	return STRING_OBJ
+}
+func (s *String) Inspect() string { return s.Value }
+
+type Error struct {
+	Message string
+}
+
+func (e *Error) Type() ObjectType { return ERROR_OBJ }
+func (e *Error) Inspect() string  { return "ERROR: " + e.Message }
+
+type ReturnValue struct {
+	Value Object
+}
+
+func (rv *ReturnValue) Type() ObjectType { return RETURN_VALUE_OBJECT }
+func (rv *ReturnValue) Inspect() string  { return rv.Value.Inspect() }
+
+type ObjectType string
+
+type Object interface {
+	Type() ObjectType
+	Inspect() string
+}
+
+type Integer struct {
+	Value int64
+}
+
+func (i *Integer) Inspect() string  { return fmt.Sprintf("%d", i.Value) }
+func (i *Integer) Type() ObjectType { return INTEGER_OBJ }
+
+type Boolean struct {
+	Value bool
+}
+
+func (b *Boolean) Type() ObjectType { return BOOLEAN_OBJ }
+func (b *Boolean) Inspect() string  { return fmt.Sprintf("%t", b.Value) }
+
+type Null struct{}
+
+func (n *Null) Type() ObjectType { return NULL_OBJ }
+func (n *Null) Inspect() string  { return "null" }
+
+type Function struct {
+	Parameters []*ast.Identifier
+	Body       *ast.BlockStatement
+	Env        *Environment
+}
+
+func (f *Function) Type() ObjectType { return FUNCTION_OBJ }
+func (f *Function) Inspect() string {
+	var out bytes.Buffer
+
+	params := []string{}
+	for _, p := range f.Parameters {
+		params = append(params, p.String())
+	}
+
+	out.WriteString("fn")
+	out.WriteString("(")
+	out.WriteString(strings.Join(params, ", "))
+	out.WriteString(") {\n")
+	out.WriteString(f.Body.String())
+	out.WriteString("\n")
+
+	return out.String()
+}
+
+type HashKey struct {
+	Type  ObjectType
+	Value uint64
+}
+
+func (b *Boolean) HashKey() HashKey {
+	var value uint64
+
+	if b.Value {
+		value = 1
+	} else {
+		value = 0
+	}
+	return HashKey{Type: b.Type(), Value: value}
+}
+
+func (i *Integer) HashKey() HashKey {
+	return HashKey{Type: i.Type(), Value: uint64(i.Value)}
+}
+
+func (s *String) HashKey() HashKey {
+	h := fnv.New64a()
+	h.Write([]byte(s.Value))
+
+	return HashKey{Type: s.Type(), Value: h.Sum64()}
+}
+
+type Hashable interface {
+	HashKey() HashKey
+}
diff --git a/object/object_test.go b/object/object_test.go
new file mode 100644
index 0000000..34d8882
--- /dev/null
+++ b/object/object_test.go
@@ -0,0 +1,22 @@
+package object
+
+import "testing"
+
+func TestStringHashKey(t *testing.T) {
+	hello1 := &String{Value: "Hello World"}
+	hello2 := &String{Value: "Hello World"}
+	diff1 := &String{Value: "My name is johnny"}
+	diff2 := &String{Value: "My name is johnny"}
+
+	if hello1.HashKey() != hello2.HashKey() {
+		t.Errorf("strings with same content have different hash keys")
+	}
+
+	if diff1.HashKey() != diff2.HashKey() {
+		t.Errorf("strings with same content have different hash keys")
+	}
+
+	if hello1.HashKey() == diff1.HashKey() {
+		t.Errorf("strings with different content have same hash keys")
+	}
+}