diff --git a/src/Area.vala b/src/Area.vala
new file mode 100644
index 0000000..5f861b6
--- /dev/null
+++ b/src/Area.vala
@@ -0,0 +1,115 @@
+namespace CairoChart {
+
+	/**
+	 * Area rectangle.
+	 */
+	[Compact]
+	public class Area {
+
+		/**
+		 * Left bound.
+		 */
+		public double x0 = 0;
+
+		/**
+		 * Top bound.
+		 */
+		public double y0 = 0;
+
+		/**
+		 * Right bound.
+		 */
+		public double x1 = 1;
+
+		/**
+		 * Bottom bound.
+		 */
+		public double y1 = 1;
+
+		/**
+		 * ``Area`` width.
+		 */
+		public double width {
+			get {
+				return x1 - x0;
+			}
+			protected set {
+				x1 = x0 + value;
+			}
+		}
+
+		/**
+		 * ``Area`` height.
+		 */
+		public double height {
+			get {
+				return y1 - y0;
+			}
+			protected set {
+				y1 = y0 + value;
+			}
+		}
+
+		/**
+		 * Constructs a new ``Area``.
+		 */
+		Area () { }
+
+		/**
+		 * Constructs a new ``Area`` with absolute coordinates.
+		 * @param x0 left bound.
+		 * @param y0 top bound.
+		 * @param x1 right bound.
+		 * @param y1 bottom bound.
+		 */
+		Area.with_abs (double x0, double y0, double x1, double y1) {
+			this.x0 = x0;
+			this.y0 = y0;
+			this.x1 = x1;
+			this.y1 = y1;
+		}
+
+		/**
+		 * Constructs a new ``Area`` with relative coordinates.
+		 * @param x0 left bound.
+		 * @param y0 top bound.
+		 * @param width ``Area`` width.
+		 * @param height ``Area`` height.
+		 */
+		Area.with_rel (double x0, double y0, double width, double height) {
+			this.x0 = x0;
+			this.y0 = y0;
+			this.width = width;
+			this.height = height;
+		}
+
+		/**
+		 * Constructs a new ``Area`` by other ``Area``.
+		 * @param area ``Area`` instance.
+		 */
+		Area.with_area (Area area) {
+			this.x0 = area.x0;
+			this.y0 = area.y0;
+			this.x1 = area.x1;
+			this.y1 = area.y0;
+		}
+
+		/**
+		 * Constructs a new ``Area`` by ``Cairo.Rectangle``.
+		 * @param rectangle ``Cairo.Rectangle`` instance.
+		 */
+		Area.with_rectangle (Cairo.Rectangle rectangle) {
+			this.x0 = rectangle.x;
+			this.y0 = rectangle.y;
+			this.width = rectangle.width;
+			this.height = rectangle.height;
+		}
+
+		/**
+		 * Gets a copy of the ``Chart``.
+		 */
+		public Area copy () {
+			return new Area.with_area(this);
+		}
+	}
+}
diff --git a/src/Range.vala b/src/Range.vala
new file mode 100644
index 0000000..1c5cf79
--- /dev/null
+++ b/src/Range.vala
@@ -0,0 +1,67 @@
+namespace CairoChart {
+
+	/**
+	 * Linear range.
+	 */
+	[Compact]
+	public class Range {
+
+		/**
+		 * Low bound.
+		 */
+		public double low = 0;
+
+		/**
+		 * High bound.
+		 */
+		public double high = 1;
+
+		/**
+		 * ``Range`` value.
+		 */
+		public double range {
+			get {
+				return high - low;
+			}
+			protected set {
+				high = low + value;
+			}
+		}
+
+		/**
+		 * Constructs a new ``Range``.
+		 */
+		Range () { }
+
+		/**
+		 * Constructs a new ``Range`` with a ``Range`` instance.
+		 */
+		Range.with_range (Range range) {
+			this.low = range.low;
+			this.high = range.high;
+		}
+
+		/**
+		 * Constructs a new ``Range`` with absolute coordinates.
+		 */
+		Range.with_abs (double low, double high) {
+			this.low = low;
+			this.high = high;
+		}
+
+		/**
+		 * Constructs a new ``Range`` with relative coordinates.
+		 */
+		Range.with_rel (double low, double range) {
+			this.low = low;
+			this.high = low + range;
+		}
+
+		/**
+		 * Gets a copy of the ``Range``.
+		 */
+		 public Range copy () {
+			return new Range.with_range(this);
+		 }
+	}
+}
diff --git a/src/Rect.vala b/src/Rect.vala
deleted file mode 100644
index 94f940c..0000000
--- a/src/Rect.vala
+++ /dev/null
@@ -1,72 +0,0 @@
-namespace CairoChart {
-
-	/**
-	 *
-	 */
-	[Compact]
-	public class Rect {
-
-		/**
-		 *
-		 */
-		public double x0 = 0;
-
-		/**
-		 *
-		 */
-		public double x1 = 1;
-
-		/**
-		 *
-		 */
-		public double y0 = 0;
-
-		/**
-		 *
-		 */
-		public double y1 = 1;
-
-		/**
-		 *
-		 */
-		public double width {
-			get {
-				return x1 - x0;
-			}
-			protected set {
-				width = value;
-				x1 = x0 + width;
-			}
-		}
-
-		/**
-		 *
-		 */
-		public double height {
-			get {
-				return y1 - y0;
-			}
-			protected set {
-				width = value;
-				y1 = y0 + height;
-			}
-		}
-
-		/**
-		 *
-		 */
-		Rect () { }
-
-		/**
-		 *
-		 */
-		Rect.with_abs () {
-		}
-
-		/**
-		 *
-		 */
-		Rect.with_rel () {
-		}
-	}
-}