diff --git a/src/agg/sum.rs b/src/agg/sum.rs
index 8ca61b4..0318665 100644
--- a/src/agg/sum.rs
+++ b/src/agg/sum.rs
@@ -1,18 +1,11 @@
 use std::marker::PhantomData;
 
-use crate::{Aggregate, EString, ParseFragment};
+use crate::{Aggregate, Aggregateble, EString, ParseFragment};
 
 #[derive(Debug, PartialEq, Eq)]
-struct Sum<R, T>(T, PhantomData<R>)
-where
-    R: Copy + std::iter::Sum,
-    T: ParseFragment + std::ops::Deref<Target = Vec<R>>;
+struct Sum<R, T>(T, PhantomData<R>);
 
-impl<R, T> Sum<R, T>
-where
-    R: Copy + std::iter::Sum,
-    T: ParseFragment + std::ops::Deref<Target = Vec<R>>,
-{
+impl<R, T> Sum<R, T> {
     fn new(inner: T) -> Self {
         Self(inner, PhantomData::default())
     }
@@ -20,8 +13,7 @@ where
 
 impl<R, T> ParseFragment for Sum<R, T>
 where
-    R: Copy + std::iter::Sum,
-    T: ParseFragment + std::ops::Deref<Target = Vec<R>>,
+    T: ParseFragment,
 {
     fn parse_frag(es: EString) -> crate::Result<Self> {
         T::parse_frag(es).map(Self::new)
@@ -30,13 +22,25 @@ where
 
 impl<R, T> Aggregate for Sum<R, T>
 where
-    R: Copy + std::iter::Sum,
-    T: ParseFragment + std::ops::Deref<Target = Vec<R>>,
+    R: std::iter::Sum,
+    T: Aggregateble<Item = R>,
 {
     type Target = R;
 
-    fn agg(&self) -> Self::Target {
-        self.0.iter().copied().sum()
+    fn agg(self) -> Self::Target {
+        self.0.items().into_iter().sum()
+    }
+}
+
+impl<R, T> Aggregateble for Sum<R, T>
+where
+    R: std::iter::Sum,
+    T: Aggregateble<Item = R>,
+{
+    type Item = R;
+
+    fn items(self) -> Vec<Self::Item> {
+        vec![self.agg()]
     }
 }
 
@@ -46,11 +50,14 @@ mod tests {
 
     use super::*;
 
+    type CommaVec<T> = SepVec<T, ','>;
+    type PlusVec<T> = SepVec<T, '+'>;
+
     #[test]
     fn should_parse_vec() {
         let es = EString::from("1,2,3");
-        match es.parse::<Sum<i32, SepVec<i32, ','>>>() {
-            Ok(res) => assert_eq!(res, Sum::new(SepVec::from(vec![1, 2, 3]))),
+        match es.parse::<Sum<i32, CommaVec<i32>>>() {
+            Ok(res) => assert_eq!(res, Sum::new(CommaVec::from(vec![1, 2, 3]))),
             _ => unreachable!(),
         }
     }
@@ -58,16 +65,23 @@ mod tests {
     #[test]
     fn should_aggregate_vector() {
         let es = EString::from("1,2,3");
-        let expr = es.parse::<Sum<i32, SepVec<i32, ','>>>().unwrap();
+        let expr = es.parse::<Sum<i32, CommaVec<i32>>>().unwrap();
         assert_eq!(expr.agg(), 6);
     }
 
+    #[test]
+    fn should_aggregate_vector_with_inner_vector() {
+        let es = EString::from("1+2,2,3");
+        let expr = es.parse::<Sum<i32, CommaVec<PlusVec<i32>>>>().unwrap();
+        assert_eq!(expr.agg(), 8);
+    }
+
     #[test]
     fn should_aggregate_vector_with_inner_aggregation() {
         let es = EString::from("1+2,2,3");
         let expr = es
-            .parse::<Sum<_, SepVec<Sum<_, SepVec<i32, '+'>>, ','>>>()
+            .parse::<Sum<_, CommaVec<Sum<_, PlusVec<i32>>>>>()
             .unwrap();
-        assert_eq!(expr.agg(), 6);
+        assert_eq!(expr.agg(), 8);
     }
 }
diff --git a/src/core.rs b/src/core.rs
index 7fbdef0..189b6c4 100644
--- a/src/core.rs
+++ b/src/core.rs
@@ -120,7 +120,13 @@ pub trait Aggregate {
     type Target: ?Sized;
 
     /// Aggregates the value.
-    fn agg(&self) -> Self::Target;
+    fn agg(self) -> Self::Target;
+}
+
+pub trait Aggregateble {
+    type Item;
+
+    fn items(self) -> Vec<Self::Item>;
 }
 
 /// Wrapper under ``String`` type.
@@ -230,6 +236,14 @@ impl ParseFragment for EString {
     }
 }
 
+impl Aggregateble for EString {
+    type Item = Self;
+
+    fn items(self) -> Vec<Self::Item> {
+        vec![self]
+    }
+}
+
 impl ParseFragment for String {
     #[inline]
     fn parse_frag(es: EString) -> crate::Result<Self> {
@@ -244,6 +258,14 @@ impl ToEString for String {
     }
 }
 
+impl Aggregateble for String {
+    type Item = Self;
+
+    fn items(self) -> Vec<Self::Item> {
+        vec![self]
+    }
+}
+
 impl ParseFragment for &'static str {
     #[inline]
     fn parse_frag(es: EString) -> crate::Result<Self> {
@@ -258,6 +280,14 @@ impl<'a> ToEString for &'a str {
     }
 }
 
+impl<'a> Aggregateble for &'a str {
+    type Item = Self;
+
+    fn items(self) -> Vec<Self::Item> {
+        vec![self]
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/std/bool.rs b/src/std/bool.rs
index b041acd..fe02c7f 100644
--- a/src/std/bool.rs
+++ b/src/std/bool.rs
@@ -1,4 +1,4 @@
-use crate::core::{EString, ParseFragment, ToEString};
+use crate::core::{Aggregateble, EString, ParseFragment, ToEString};
 use crate::error::{Error, Reason};
 
 impl ParseFragment for bool {
@@ -19,6 +19,14 @@ impl ToEString for bool {
     }
 }
 
+impl Aggregateble for bool {
+    type Item = Self;
+
+    fn items(self) -> Vec<Self::Item> {
+        vec![self]
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/std/number.rs b/src/std/number.rs
index 44d2f0e..4c6a982 100644
--- a/src/std/number.rs
+++ b/src/std/number.rs
@@ -1,4 +1,4 @@
-use crate::core::{EString, ParseFragment, ToEString};
+use crate::core::{Aggregateble, EString, ParseFragment, ToEString};
 use crate::error::{Error, Reason};
 
 #[doc(hidden)]
@@ -18,6 +18,14 @@ macro_rules! from_env_string_numbers_impl {
                     EString(self.to_string())
                 }
             }
+
+            impl Aggregateble for $ty {
+                type Item = Self;
+
+                fn items(self) -> Vec<Self::Item> {
+                    vec![self]
+                }
+            }
         )+
     };
 }
diff --git a/src/std/option.rs b/src/std/option.rs
index 191ad39..bea98b5 100644
--- a/src/std/option.rs
+++ b/src/std/option.rs
@@ -1,4 +1,4 @@
-use crate::core::{EString, ParseFragment, ToEString};
+use crate::core::{Aggregateble, EString, ParseFragment, ToEString};
 
 impl<T> ToEString for Option<T>
 where
@@ -25,6 +25,17 @@ where
     }
 }
 
+impl<T> Aggregateble for Option<T>
+where
+    T: Aggregateble,
+{
+    type Item = T::Item;
+
+    fn items(self) -> Vec<Self::Item> {
+        self.map(T::items).unwrap_or_default()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/structs/sep_vec.rs b/src/structs/sep_vec.rs
index 1208642..59c0eb7 100644
--- a/src/structs/sep_vec.rs
+++ b/src/structs/sep_vec.rs
@@ -1,7 +1,7 @@
 //! Contains the implementations to vec type
 //!
 
-use crate::core::{EString, ParseFragment, ToEString};
+use crate::core::{Aggregateble, EString, ParseFragment, ToEString};
 use std::fmt::Write;
 
 /// Wrapper for ``Vec`` to split string by a separator (`SEP`).
@@ -92,17 +92,25 @@ where
     }
 }
 
+impl<T, const SEP: char> Aggregateble for SepVec<T, SEP>
+where
+    T: Aggregateble,
+{
+    type Item = T::Item;
+
+    fn items(self) -> Vec<Self::Item> {
+        self.0.into_iter().flat_map(T::items).collect()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
     use crate::Pair;
     use crate::{Error, Reason};
 
-    const COMMA: char = ',';
-    const SEMI: char = ';';
-
-    type CommaVec<T> = SepVec<T, COMMA>;
-    type SemiVec<T> = SepVec<T, SEMI>;
+    type CommaVec<T> = SepVec<T, ','>;
+    type SemiVec<T> = SepVec<T, ';'>;
 
     #[test]
     fn should_parse_into_vec() {
@@ -171,4 +179,18 @@ d,e";
         let vec = SepVec::<_, ','>::from(vec![PlusPair::from((1, 2)), PlusPair::from((3, 4))]);
         assert_eq!(vec.to_estring(), EString(String::from("1+2,3+4")));
     }
+
+    #[test]
+    fn should_returns_aggregatable_items() {
+        let estr = EString::from("1,2,3,4,5");
+        let res = estr.parse::<CommaVec<i32>>().unwrap();
+        assert_eq!(res.items(), vec![1, 2, 3, 4, 5]);
+    }
+
+    #[test]
+    fn should_returns_flatten_aggregatable_items() {
+        let estr = EString::from("1,2; 3,4,5; 6,7");
+        let res = estr.parse::<SemiVec<CommaVec<i32>>>().unwrap();
+        assert_eq!(res.items(), vec![1, 2, 3, 4, 5, 6, 7]);
+    }
 }