diff --git a/src/Application.hpp b/src/Application.hpp
index b2cf02e..4ed7b95 100644
--- a/src/Application.hpp
+++ b/src/Application.hpp
@@ -4,15 +4,25 @@ class Bus;
 class Window;
 class Debugger;
 
+/**
+ * @brief Contains the program loop and invokes other objects update functions.
+ */
 class Application
 {
 public:
+	/**
+	 * @brief Create and launch a new application.
+	 */
 	static void Launch();
 
 private:
 	Application();
 	~Application();
 
+	/**
+	 * @brief Update the application.
+	 * This includes polling events, ticking the emulator and rendering
+	 */
 	bool Update();
 
 private:
diff --git a/src/Bus.hpp b/src/Bus.hpp
index cfcfbaa..4cd0006 100644
--- a/src/Bus.hpp
+++ b/src/Bus.hpp
@@ -7,6 +7,14 @@
 #include "PPU.hpp"
 #include "Cartridge.hpp"
 
+/**
+ * @brief The main bus for hardware to communicate.
+ * 
+ * This is not a realistic representation of the NES's bus, as the
+ * CPU and PPU don't share a bus in the real world. However this
+ * bus class still doesn't give the CPU/PPU direct access to the other
+ * components address space.
+ */
 class Bus
 {
 	friend class Debugger;
@@ -16,18 +24,60 @@ class Bus
 public:
 	Bus();
 
+	/**
+	 * @brief Reboot the NES.
+	 * 
+	 * This equates to turning the NES off and on again.
+	 * Internal state will be equal to the powerup state
+	 */
 	void Reboot();
+
+	/**
+	 * @brief Resets the NES.
+	 *
+	 * Internal state will be equal to the reset state
+	 */
 	void Reset();
 
+	/**
+	 * @brief Advance the emulator by one CPU cycle (and 3 PPU cycles).
+	 */
 	uint8_t Tick();
+
+	/**
+	 * @brief Advance the emulator by one CPU instruction.
+	 */
 	bool Instruction();
+
+	/**
+	 * @brief Advance the emulator by one Frame.
+	 * The emulator runs until the PPU triggers VBlankStart
+	 */
 	bool Frame();
 
+	/**
+	 * @brief Read call from the CPU
+	 */
 	Byte ReadCPU(Word addr);
+
+	/**
+	 * @brief Read call from the PPU
+	 */
 	Byte ReadPPU(Word addr);
+
+	/**
+	 * @brief Write call from the CPU
+	 */
 	void WriteCPU(Word addr, Byte val);
+
+	/**
+	 * @brief Write call from the PPU
+	 */
 	void WritePPU(Word addr, Byte val);
 
+	/**
+	 * @brief Lets the PPU trigger NMIs.
+	 */
 	inline void NMI() { cpu.NMI(); }
 
 private: