diff --git a/Cargo.toml b/Cargo.toml
index 8c6eecb..c487530 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -12,7 +12,10 @@ default = ["console_error_panic_hook"]
 
 [dependencies]
 wasm-bindgen = "0.2.84"
-chrono = { version = "0.4.31", features = [ "clock" ] }
+chrono = { version = "0.4.31", features = [ "clock", "serde" ] }
+serde = { version = "1.0", features = [ "derive" ] }
+serde_json = { version = "1.0", features = [ "std" ] }
+serde_with = { version = "3.4.0", features = [ "std", "chrono_0_4", "json" ] }
 
 # The `console_error_panic_hook` crate provides better debugging of panics by
 # logging them with `console.error`. This is great for development, but requires
diff --git a/src/db.rs b/src/db.rs
new file mode 100644
index 0000000..c6b68ef
--- /dev/null
+++ b/src/db.rs
@@ -0,0 +1,37 @@
+pub mod json;
+
+use crate::models::*;
+use std::io;
+use serde_json;
+
+#[derive(Debug)]
+pub enum Error {
+    Generic(String),
+    FsIo(String),
+    Json(String),
+}
+
+impl From<io::Error> for Error {
+    fn from(e: io::Error) -> Self {
+        Self::FsIo(e.to_string())
+    }
+}
+
+impl From<serde_json::Error> for Error {
+    fn from(e: serde_json::Error) -> Self{
+        Self::Json(e.to_string())
+    }
+}
+
+pub trait Storage {
+    fn add_category(&mut self, category: NewCategory) -> Result<i32, Error>;
+    fn add_series(&mut self, category_id: i32, series: NewSeries) -> Result<i32, Error>;
+    fn add_series_point(&mut self, category_id: i32, series_id: i32, series_point: NewSeriesPoint) -> Result<i32, Error>;
+    //fn add_user(&mut self, id: i32, user: NewUser) -> Result<User, Error>;
+    fn get_category(&self, id: i32) -> Option<Category>;
+    //fn get_series(&self, id: i32) -> Result<Series, Error>;
+    //fn get_user(&self, id: i32) -> Result<User, Error>;
+    //fn update_category(&mut self, id: i32, changeset: CategoryChangeset) -> Result<(), Error>;
+    //fn update_series(&mut self, id: i32, changeset: SeriesChangeset) -> Result<(), Error>;
+    //fn update_user(&mut self, id: i32, changeset: UserChangeset) -> Result<(), Error>;
+}
diff --git a/src/db/json.rs b/src/db/json.rs
new file mode 100644
index 0000000..0734acc
--- /dev/null
+++ b/src/db/json.rs
@@ -0,0 +1,136 @@
+use super::*;
+
+pub struct JsonDb {
+    pub value: String,
+}
+
+/// JsonDb is single user.
+impl JsonDb {
+    pub fn new(value: Option<String>) -> Self {
+        match value {
+            Some(value) => JsonDb { value },
+            None => JsonDb { value: String::from("[]") },
+        }
+    }
+
+    fn load(&self) -> Result<Vec<Category>, Error> {
+        match serde_json::from_str::<Vec<Category>>(&self.value) {
+            Ok(d) => Ok(d),
+            Err(e) => Err(Error::from(e)),
+        }
+    }
+
+    fn save(&mut self, data: Vec<Category>) -> Result<(), Error> {
+        let data = serde_json::to_string_pretty(&data);
+        match data {
+            Ok(d) => {
+                self.value = d;
+                Ok(())
+            },
+            Err(e) => Err(Error::from(e)),
+        }
+    }
+}
+
+impl Storage for JsonDb {
+    fn add_category(&mut self, category: NewCategory) -> Result<i32, Error> {
+        let mut max_id = 1;
+        let mut data = self.load()?;
+        for cat in data.iter().clone() {
+            if cat.id > max_id {
+                max_id = cat.id
+            }
+        }
+        let created = Category::new(max_id+1, category);
+        data.push(created);
+        self.save(data)?;
+
+        Ok(max_id + 1)
+    }
+
+    fn add_series(&mut self, category_id: i32, series: NewSeries) -> Result<i32, Error> {
+        let mut max_id = 1;
+        let mut cat: Option<&mut Category> = None;
+
+        let mut data = self.load()?;
+        for cat_opt in data.iter_mut() {
+            if cat_opt.id == category_id {
+                cat = Some(cat_opt);
+                break;
+            }
+        }
+
+        if let None = cat {
+            return Err(Error::Generic ("Unable to find category".to_owned()));
+        }
+        let cat = cat.unwrap();
+
+
+        for series in cat.series.iter().clone() {
+            if series.id > max_id {
+                max_id = series.id;
+            }
+        }
+
+        let created = Series::new(max_id+1, series);
+        cat.series.push(created);
+        self.save(data)?;
+
+        Ok(max_id + 1)
+    }
+
+    fn add_series_point(&mut self, category_id: i32, series_id: i32, series_point: NewSeriesPoint) -> Result<i32, Error> {
+        let mut max_id = 1;
+        let mut cat: Option<&mut Category> = None;
+        let mut series: Option<&mut Series> = None;
+
+        let mut data = self.load()?;
+        for cat_opt in data.iter_mut() {
+            if cat_opt.id == category_id {
+                cat = Some(cat_opt);
+                break;
+            }
+        }
+
+        if let None = cat {
+            return Err(Error::Generic ("Unable to find category".to_owned()));
+        }
+        let cat = cat.unwrap();
+
+        for series_opt in cat.series.iter_mut() {
+            if series_opt.id == series_id {
+                series = Some(series_opt);
+                break;
+            }
+        }
+
+        if let None = series {
+            return Err(Error::Generic ("Unable to find series".to_owned()));
+        }
+        let series: &mut Series = series.unwrap();
+
+        for point in series.points.iter().clone() {
+            if point.id > max_id {
+                max_id = point.id;
+            }
+        }
+
+        let created = SeriesPoint::new(max_id + 1, series_point);
+        series.points.push(created);
+        self.save(data)?;
+
+        Ok(max_id + 1)
+    }
+
+    fn get_category(&self, id: i32) -> Option<Category> {
+        let data = self.load().ok()?;
+
+        for cat_opt in data {
+            if cat_opt.id == id {
+                return Some(cat_opt);
+            }
+        }
+
+        None
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
index 16bcb9b..8be5d85 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
 mod utils;
 pub mod models;
+pub mod db;
 
 use wasm_bindgen::prelude::*;
diff --git a/src/models.rs b/src/models.rs
index 55eb925..35b6a22 100644
--- a/src/models.rs
+++ b/src/models.rs
@@ -1,9 +1,11 @@
-pub mod category;
-pub mod series;
-pub mod series_point;
-pub mod series_type;
+mod category;
+mod series;
+mod series_point;
+mod series_type;
+mod user;
 
 pub use category::*;
 pub use series::*;
 pub use series_point::*;
 pub use series_type::*;
+pub use user::*;
diff --git a/src/models/category.rs b/src/models/category.rs
index fb0c245..dc36e9b 100644
--- a/src/models/category.rs
+++ b/src/models/category.rs
@@ -1,18 +1,19 @@
 use crate::models::Series;
+use serde::{ Serialize, Deserialize };
 
-#[derive(Debug)]
+#[derive(Debug, Serialize, Deserialize)]
 pub struct Category {
-    id: i32,
-    name: String,
-    series: Vec<Series>,
+    pub id: i32,
+    pub name: String,
+    pub series: Vec<Series>,
 }
 
 impl Category {
-    pub fn new(id: i32, name: String) -> Category {
+    pub fn new(id: i32, new: NewCategory) -> Category {
         Category {
             id,
-            name,
-            series: vec![],
+            name: new.name,
+            series: new.series,
         }
     }
 
@@ -20,3 +21,13 @@ impl Category {
         self.series.push(series);
     }
 }
+
+pub struct CategoryChangeset {
+    pub name: Option<String>,
+    pub series: Option<Vec<Series>>,
+}
+
+pub struct NewCategory {
+    pub name: String,
+    pub series: Vec<Series>,
+}
diff --git a/src/models/series.rs b/src/models/series.rs
index 1c61d88..aa3e043 100644
--- a/src/models/series.rs
+++ b/src/models/series.rs
@@ -1,23 +1,27 @@
 use chrono;
 use super::series_point::SeriesPoint;
+use serde::{ Serialize, Deserialize };
+use serde_with;
 
-#[derive(Debug)]
+#[serde_with::serde_as]
+#[derive(Debug, Serialize, Deserialize)]
 pub struct Series {
-    id: i32,
-    name: String,
-    repeat: chrono::Duration,
-    good: bool,
-    points: Vec<SeriesPoint>,
+    pub id: i32,
+    pub name: String,
+    #[serde_as(as = "serde_with::DurationSeconds<i64>")]
+    pub repeat: chrono::Duration,
+    pub good: bool,
+    pub points: Vec<SeriesPoint>,
 }
 
 impl Series {
-    pub fn new(id: i32, name: String, repeat: chrono::Duration, good: bool) -> Series {
+    pub fn new(id: i32, series: NewSeries) -> Series {
         Series {
             id,
-            name,
-            repeat,
-            good,
-            points: vec![],
+            name: series.name,
+            repeat: series.repeat,
+            good: series.good,
+            points: series.points,
         }
     }
 
@@ -25,3 +29,17 @@ impl Series {
         self.points.push(point);
     }
 }
+
+pub struct SeriesChangeset {
+    pub name: Option<String>,
+    pub repeat: Option<chrono::Duration>,
+    pub good: Option<bool>,
+    pub points: Option<Vec<SeriesPoint>>,
+}
+
+pub struct NewSeries {
+    pub name: String,
+    pub repeat: chrono::Duration,
+    pub good: bool,
+    pub points: Vec<SeriesPoint>,
+}
diff --git a/src/models/series_point.rs b/src/models/series_point.rs
index 55bfbd7..4eac7d3 100644
--- a/src/models/series_point.rs
+++ b/src/models/series_point.rs
@@ -1,19 +1,25 @@
 use chrono;
 use super::series_type::SeriesType;
+use serde::{ Serialize, Deserialize };
 
-#[derive(Debug)]
+#[derive(Debug, Serialize, Deserialize)]
 pub struct SeriesPoint {
-    id: i32,
-    timestamp: chrono::NaiveDateTime,
-    value: SeriesType,
+    pub id: i32,
+    pub timestamp: chrono::NaiveDateTime,
+    pub value: SeriesType,
 }
 
 impl SeriesPoint {
-    pub fn new(id: i32, timestamp: chrono::NaiveDateTime, value: SeriesType) -> SeriesPoint {
+    pub fn new(id: i32, new: NewSeriesPoint) -> SeriesPoint {
         SeriesPoint {
             id,
-            timestamp,
-            value
+            timestamp: new.timestamp,
+            value: new.value,
         }
     }
 }
+
+pub struct NewSeriesPoint {
+    pub timestamp: chrono::NaiveDateTime,
+    pub value: SeriesType,
+}
diff --git a/src/models/series_type.rs b/src/models/series_type.rs
index 26a13be..64cf626 100644
--- a/src/models/series_type.rs
+++ b/src/models/series_type.rs
@@ -1,4 +1,6 @@
-#[derive(Debug)]
+use serde::{ Serialize, Deserialize };
+
+#[derive(Debug, Serialize, Deserialize)]
 pub enum SeriesType {
     Bool(bool),
     Count(u32),
diff --git a/src/models/user.rs b/src/models/user.rs
new file mode 100644
index 0000000..1366763
--- /dev/null
+++ b/src/models/user.rs
@@ -0,0 +1,18 @@
+use serde::{ Serialize, Deserialize };
+
+#[derive(Debug, Serialize, Deserialize)]
+pub struct User {
+    id: i32,
+    name: String,
+    email: String,
+}
+
+pub struct UserChangeset {
+    name: Option<String>,
+    email: Option<String>,
+}
+
+pub struct NewUser {
+    name: String,
+    email: String,
+}