diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,10 @@
+# 0.1.1.0
+
+- Add `gconIndex`
+- Interface for constructor tags
+- Type-level `Meta` accessors
+- Add basic `Newtype` functions
+
+# 0.1.0.0
+
+Released generic-data
diff --git a/generic-data.cabal b/generic-data.cabal
--- a/generic-data.cabal
+++ b/generic-data.cabal
@@ -1,5 +1,5 @@
 name:                generic-data
-version:             0.1.0.0
+version:             0.1.1.0
 synopsis:            Utilities for GHC.Generics
 description:         This package provides common functions on generic types.
                      See README.
@@ -11,7 +11,7 @@
 copyright:           2018 Li-yao Xia
 category:            Other
 build-type:          Simple
-extra-source-files:  README.md
+extra-source-files:  README.md, CHANGELOG.md
 cabal-version:       >=1.10
 tested-with:         GHC == 8.0.2, GHC == 8.2.2
 
@@ -25,6 +25,7 @@
     Generic.Data.Internal.Defun
     Generic.Data.Internal.Enum
     Generic.Data.Internal.Functions
+    Generic.Data.Internal.Generically
     Generic.Data.Internal.Meta
     Generic.Data.Internal.Newtype
     Generic.Data.Internal.Prelude
diff --git a/src/Generic/Data.hs b/src/Generic/Data.hs
--- a/src/Generic/Data.hs
+++ b/src/Generic/Data.hs
@@ -88,10 +88,16 @@
   , Opaque(..)
   , Opaque1(..)
 
-    -- * Newtypes
+    -- * Carriers of generic instances
   , Generically(..)
   , Generically1(..)
 
+    -- * Newtype
+    -- | Generic pack/unpack.
+  , Newtype
+  , pack
+  , unpack
+
     -- * Accessing metadata
 
     -- | Using @TypeApplications@.
@@ -108,12 +114,36 @@
   , gconFixity
   , gconIsRecord
   , gconNum
+  , gconIndex
   , Constructors
   , GConstructors
+
+    -- *** Constructor tags
+  , ConId()
+  , conId
+  , conIdToInt
+  , conIdToString
+  , conIdEnum
+
+  -- ** Using type families
+  , MetaOf
+  , MetaDataName
+  , MetaDataModule
+  , MetaDataPackage
+  , MetaDataNewtype
+  , MetaConsName
+  , MetaConsFixity
+  , MetaConsRecord
+  , MetaSelNameM
+  , MetaSelName
+  , MetaSelUnpack
+  , MetaSelSourceStrictness
+  , MetaSelStrictness
   ) where
 
 import Generic.Data.Internal.Prelude
 import Generic.Data.Internal.Enum
+import Generic.Data.Internal.Generically
 import Generic.Data.Internal.Meta
 import Generic.Data.Internal.Show
 import Generic.Data.Internal.Newtype
diff --git a/src/Generic/Data/Internal/Generically.hs b/src/Generic/Data/Internal/Generically.hs
new file mode 100644
--- /dev/null
+++ b/src/Generic/Data/Internal/Generically.hs
@@ -0,0 +1,103 @@
+-- | Newtypes with instances implemented using generic combinators.
+
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE UndecidableInstances #-}
+
+module Generic.Data.Internal.Generically where
+
+import Control.Applicative
+import Data.Functor.Classes
+import Data.Semigroup
+import GHC.Generics
+
+import Generic.Data.Internal.Prelude
+import Generic.Data.Internal.Enum
+import Generic.Data.Internal.Show
+
+-- | Type with instances derived via 'Generic'.
+newtype Generically a = Generically { unGenerically :: a }
+
+instance Generic a => Generic (Generically a) where
+  type Rep (Generically a) = Rep a
+  to = Generically . to
+  from = from . unGenerically
+
+instance (Generic a, Eq (Rep a ())) => Eq (Generically a) where
+  (==) = geq
+
+instance (Generic a, Ord (Rep a ())) => Ord (Generically a) where
+  compare = gcompare
+
+instance (Generic a, GShow0 (Rep a)) => Show (Generically a) where
+  showsPrec = gshowsPrec
+
+instance (Generic a, Semigroup (Rep a ())) => Semigroup (Generically a) where
+  (<>) = gmappend
+
+instance (Generic a, Monoid (Rep a ())) => Monoid (Generically a) where
+  mempty = gmempty
+  mappend = gmappend'
+
+instance (Generic a, GEnum (Rep a)) => Enum (Generically a) where
+  fromEnum = gfromEnum
+  toEnum = gtoEnum
+
+instance (Generic a, GBounded (Rep a)) => Bounded (Generically a) where
+  minBound = gminBound
+  maxBound = gmaxBound
+
+-- | Type with instances derived via 'Generic1'.
+newtype Generically1 f a = Generically1 { unGenerically1 :: f a }
+
+instance Generic (f a) => Generic (Generically1 f a) where
+  type Rep (Generically1 f a) = Rep (f a)
+  to = Generically1 . to
+  from = from . unGenerically1
+
+instance Generic1 f => Generic1 (Generically1 f) where
+  type Rep1 (Generically1 f) = Rep1 f
+  to1 = Generically1 . to1
+  from1 = from1 . unGenerically1
+
+instance (Generic1 f, Eq1 (Rep1 f)) => Eq1 (Generically1 f) where
+  liftEq = gliftEq
+
+instance (Generic1 f, Eq1 (Rep1 f), Eq a) => Eq (Generically1 f a) where
+  (==) = eq1
+
+instance (Generic1 f, Ord1 (Rep1 f)) => Ord1 (Generically1 f) where
+  liftCompare = gliftCompare
+
+instance (Generic1 f, Ord1 (Rep1 f), Ord a) => Ord (Generically1 f a) where
+  compare = compare1
+
+instance (Generic1 f, GShow1 (Rep1 f)) => Show1 (Generically1 f) where
+  liftShowsPrec = gliftShowsPrec
+
+instance (Generic1 f, GShow1 (Rep1 f), Show a) => Show (Generically1 f a) where
+  showsPrec = showsPrec1
+
+instance (Generic1 f, Functor (Rep1 f)) => Functor (Generically1 f) where
+  fmap = gfmap
+  (<$) = gconstmap
+
+instance (Generic1 f, Applicative (Rep1 f)) => Applicative (Generically1 f) where
+  pure = gpure
+  (<*>) = gap
+#if MIN_VERSION_base(4,10,0)
+  liftA2 = gliftA2
+#endif
+
+instance (Generic1 f, Alternative (Rep1 f)) => Alternative (Generically1 f) where
+  empty = gempty
+  (<|>) = galt
+
+instance (Generic1 f, Foldable (Rep1 f)) => Foldable (Generically1 f) where
+  foldMap = gfoldMap
+  foldr = gfoldr
+
+instance (Generic1 f, Traversable (Rep1 f)) => Traversable (Generically1 f) where
+  traverse = gtraverse
+  sequenceA = gsequenceA
diff --git a/src/Generic/Data/Internal/Meta.hs b/src/Generic/Data/Internal/Meta.hs
--- a/src/Generic/Data/Internal/Meta.hs
+++ b/src/Generic/Data/Internal/Meta.hs
@@ -5,6 +5,7 @@
 {-# OPTIONS_GHC -Wno-simplifiable-class-constraints #-}
 
 {-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE FlexibleContexts #-}
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE PolyKinds #-}
@@ -18,6 +19,7 @@
 
 import Data.Proxy
 import GHC.Generics
+import GHC.TypeLits (Symbol)
 
 -- | Name of the first data constructor in a type as a string.
 --
@@ -98,24 +100,47 @@
 gconNum :: forall a. Constructors a => Int
 gconNum = gConNum @(Rep a)
 
+-- | Index of a constructor.
+--
+-- @
+-- 'gconIndex' Nothing = 0
+-- 'gconIndex' (Just "test") = 1
+-- @
+gconIndex :: forall a. Constructors a => a -> Int
+gconIndex = conIdToInt . conId
+
 -- | An opaque identifier for a constructor.
 newtype ConId a = ConId Int
   deriving (Eq, Ord)
 
+-- | Identifier of a constructor.
+conId :: forall a. Constructors a => a -> ConId a
+conId = toConId . gConId . from
+
+-- | Index of a constructor, given its identifier.
+-- See also 'gconIndex'.
 conIdToInt :: forall a. ConId a -> Int
 conIdToInt (ConId i) = i
 
+-- | Name of a constructor. See also 'gconName'.
+conIdToString :: forall a. Constructors a => ConId a -> String
+conIdToString = gConIdToString . fromConId
+
+-- | All constructor identifiers.
+--
+-- @
+-- 'gconNum' \@a = length ('conIdEnum' \@a)
+-- @
 conIdEnum :: forall a. Constructors a => [ConId a]
 conIdEnum = fmap ConId [0 .. n]
   where
     ConId n = conIdMax @a
 
-conIdToString :: forall a. Constructors a => ConId a -> String
-conIdToString = gConIdToString . fromConId
-
-conId :: forall a. Constructors a => a -> ConId a
-conId = toConId . gConId . from
+-- | This must not be called on an empty type.
+conIdMin :: forall a. Constructors a => ConId a
+conIdMin = ConId 0
 
+-- | This must not be called on an empty type.
 conIdMax :: forall a. Constructors a => ConId a
 conIdMax = toConId gConIdMax
 
@@ -138,6 +163,9 @@
 reGConId :: GConId r -> GConId s
 reGConId (GConId i) = GConId i
 
+gConIdMin :: forall r. GConstructors r => GConId r
+gConIdMin = GConId 0
+
 gConIdMax :: forall r. GConstructors r => GConId r
 gConIdMax = GConId (gConNum @r - 1)
 
@@ -180,3 +208,59 @@
   gConNum = 1
   gConFixity = conFixity
   gConIsRecord = conIsRecord
+
+-- * Type families
+
+-- | 'Meta' field of the 'M1' type constructor.
+type family MetaOf (f :: * -> *) :: Meta where
+  MetaOf (M1 i d f) = d
+
+-- Variable names borrowed from the documentation on 'Meta'.
+
+-- | Name of the data type ('MetaData').
+type family MetaDataName (m :: Meta) :: Symbol where
+  MetaDataName ('MetaData n _m _p _nt) = n
+
+-- | Name of the module where the data type is defined ('MetaData')
+type family MetaDataModule (m :: Meta) :: Symbol where
+  MetaDataModule ('MetaData _n m _p _nt) = m
+
+-- | Name of the package where the data type is defined ('MetaData')
+type family MetaDataPackage (m :: Meta) :: Symbol where
+  MetaDataPackage ('MetaData _n _m p _nt) = p
+
+-- | @True@ if the data type is a newtype ('MetaData').
+type family MetaDataNewtype (m :: Meta) :: Bool where
+  MetaDataNewtype ('MetaData _n _m _p nt) = nt
+
+-- | Name of the constructor ('MetaCons').
+type family MetaConsName (m :: Meta) :: Symbol where
+  MetaConsName ('MetaCons n _f _s) = n
+
+-- | Fixity of the constructor ('MetaCons').
+type family MetaConsFixity (m :: Meta) :: FixityI where
+  MetaConsFixity ('MetaCons _n f s) = f
+
+-- | @True@ for a record constructor ('MetaCons').
+type family MetaConsRecord (m :: Meta) :: Bool where
+  MetaConsRecord ('MetaCons _n _f s) = s
+
+-- | @Just@ the name of the record field, if it is one ('MetaSel').
+type family MetaSelNameM (m :: Meta) :: Maybe Symbol where
+  MetaSelNameM ('MetaSel mn _su _ss _ds) = mn
+
+-- | Name of the record field; undefined for non-record fields ('MetaSel').
+type family MetaSelName (m :: Meta) :: Symbol where
+  MetaSelName ('MetaSel ('Just n) _su _ss _ds) = n
+
+-- | Unpackedness annotation of a field ('MetaSel').
+type family MetaSelUnpack (m :: Meta) :: SourceUnpackedness where
+  MetaSelUnpack ('MetaSel _mn su _ss _ds) = su
+
+-- | Strictness annotation of a field ('MetaSel').
+type family MetaSelSourceStrictness (m :: Meta) :: SourceStrictness where
+  MetaSelSourceStrictness ('MetaSel _mn _su ss _ds) = ss
+
+-- | Inferred strictness of a field ('MetaSel').
+type family MetaSelStrictness (m :: Meta) :: DecidedStrictness where
+  MetaSelStrictness ('MetaSel _mn _su _ss ds) = ds
diff --git a/src/Generic/Data/Internal/Newtype.hs b/src/Generic/Data/Internal/Newtype.hs
--- a/src/Generic/Data/Internal/Newtype.hs
+++ b/src/Generic/Data/Internal/Newtype.hs
@@ -1,103 +1,43 @@
--- | Newtypes with instances implemented using generic combinators.
-
-{-# LANGUAGE CPP #-}
+{-# LANGUAGE ConstraintKinds #-}
+{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE TypeOperators #-}
 {-# LANGUAGE UndecidableInstances #-}
-
-module Generic.Data.Internal.Newtype where
-
-import Control.Applicative
-import Data.Functor.Classes
-import Data.Semigroup
-import GHC.Generics
-
-import Generic.Data.Internal.Prelude
-import Generic.Data.Internal.Enum
-import Generic.Data.Internal.Show
-
--- | Type with instances derived via 'Generic'.
-newtype Generically a = Generically { unGenerically :: a }
-
-instance Generic a => Generic (Generically a) where
-  type Rep (Generically a) = Rep a
-  to = Generically . to
-  from = from . unGenerically
-
-instance (Generic a, Eq (Rep a ())) => Eq (Generically a) where
-  (==) = geq
-
-instance (Generic a, Ord (Rep a ())) => Ord (Generically a) where
-  compare = gcompare
-
-instance (Generic a, GShow0 (Rep a)) => Show (Generically a) where
-  showsPrec = gshowsPrec
-
-instance (Generic a, Semigroup (Rep a ())) => Semigroup (Generically a) where
-  (<>) = gmappend
-
-instance (Generic a, Monoid (Rep a ())) => Monoid (Generically a) where
-  mempty = gmempty
-  mappend = gmappend'
-
-instance (Generic a, GEnum (Rep a)) => Enum (Generically a) where
-  fromEnum = gfromEnum
-  toEnum = gtoEnum
-
-instance (Generic a, GBounded (Rep a)) => Bounded (Generically a) where
-  minBound = gminBound
-  maxBound = gmaxBound
-
--- | Type with instances derived via 'Generic1'.
-newtype Generically1 f a = Generically1 { unGenerically1 :: f a }
-
-instance Generic (f a) => Generic (Generically1 f a) where
-  type Rep (Generically1 f a) = Rep (f a)
-  to = Generically1 . to
-  from = from . unGenerically1
-
-instance Generic1 f => Generic1 (Generically1 f) where
-  type Rep1 (Generically1 f) = Rep1 f
-  to1 = Generically1 . to1
-  from1 = from1 . unGenerically1
+{-# LANGUAGE UndecidableSuperClasses #-}
 
-instance (Generic1 f, Eq1 (Rep1 f)) => Eq1 (Generically1 f) where
-  liftEq = gliftEq
+-- | Pack/unpack newtypes.
 
-instance (Generic1 f, Eq1 (Rep1 f), Eq a) => Eq (Generically1 f a) where
-  (==) = eq1
+module Generic.Data.Internal.Newtype where
 
-instance (Generic1 f, Ord1 (Rep1 f)) => Ord1 (Generically1 f) where
-  liftCompare = gliftCompare
+import Data.Coerce (Coercible, coerce)
+import Data.Kind (Constraint)
+import GHC.Generics (Generic(..), D1, C1, S1, K1)
+import GHC.TypeLits (TypeError, ErrorMessage(..))
 
-instance (Generic1 f, Ord1 (Rep1 f), Ord a) => Ord (Generically1 f a) where
-  compare = compare1
+import Generic.Data.Internal.Meta (MetaDataNewtype, MetaOf)
 
-instance (Generic1 f, GShow1 (Rep1 f)) => Show1 (Generically1 f) where
-  liftShowsPrec = gliftShowsPrec
+-- | Class of newtypes.
+class (Generic a, Coercible a (Old a), Newtype' a) => Newtype a
+instance (Generic a, Coercible a (Old a), Newtype' a) => Newtype a
 
-instance (Generic1 f, GShow1 (Rep1 f), Show a) => Show (Generically1 f a) where
-  showsPrec = showsPrec1
+type Old a = GOld (Rep a)
 
-instance (Generic1 f, Functor (Rep1 f)) => Functor (Generically1 f) where
-  fmap = gfmap
-  (<$) = gconstmap
+type family GOld (f :: * -> *) where
+  GOld (D1 _d (C1 _c (S1 _s (K1 _i b)))) = b
 
-instance (Generic1 f, Applicative (Rep1 f)) => Applicative (Generically1 f) where
-  pure = gpure
-  (<*>) = gap
-#if MIN_VERSION_base(4,10,0)
-  liftA2 = gliftA2
-#endif
+type Newtype' a = NewtypeErr a (MetaDataNewtype (MetaOf (Rep a)))
 
-instance (Generic1 f, Alternative (Rep1 f)) => Alternative (Generically1 f) where
-  empty = gempty
-  (<|>) = galt
+type family NewtypeErr a (b :: Bool) :: Constraint where
+  NewtypeErr a 'True = ()
+  NewtypeErr a 'False = TypeError
+    ('Text "The type " ':<>: 'ShowType a ':<>: 'Text " is not a newtype.")
 
-instance (Generic1 f, Foldable (Rep1 f)) => Foldable (Generically1 f) where
-  foldMap = gfoldMap
-  foldr = gfoldr
+-- | Generic newtype destructor.
+unpack :: Newtype a => a -> Old a
+unpack = coerce
 
-instance (Generic1 f, Traversable (Rep1 f)) => Traversable (Generically1 f) where
-  traverse = gtraverse
-  sequenceA = gsequenceA
+-- | Generic newtype constructor.
+pack :: Newtype a => Old a -> a
+pack = coerce
diff --git a/src/Generic/Data/Internal/Show.hs b/src/Generic/Data/Internal/Show.hs
--- a/src/Generic/Data/Internal/Show.hs
+++ b/src/Generic/Data/Internal/Show.hs
@@ -31,6 +31,7 @@
 -- | Generic representation of 'Show' types.
 type GShow0 = GShow Proxy
 
+-- | Generic 'liftShowsPrec'.
 gliftShowsPrec
   :: (Generic1 f, GShow1 (Rep1 f))
   => (Int -> a -> ShowS) -> ([a] -> ShowS)