diff --git a/src/component.rs b/src/component.rs
new file mode 100644
index 0000000..059730b
--- /dev/null
+++ b/src/component.rs
@@ -0,0 +1,5 @@
+mod stack;
+mod timer;
+
+pub use stack::*;
+pub use timer::*;
diff --git a/src/component/stack.rs b/src/component/stack.rs
new file mode 100644
index 0000000..3464c00
--- /dev/null
+++ b/src/component/stack.rs
@@ -0,0 +1,62 @@
+use crate::EffectMergeRegistry;
+use bevy_app::{App, Plugin};
+use bevy_ecs::prelude::ReflectComponent;
+use bevy_ecs::prelude::{Component, Entity, EntityWorldMut};
+use bevy_reflect::prelude::ReflectDefault;
+use bevy_reflect::Reflect;
+use std::ops::{Add, AddAssign, Deref, DerefMut};
+
+pub(crate) struct StackPlugin;
+
+impl Plugin for StackPlugin {
+    fn build(&self, app: &mut App) {
+        app.world_mut()
+            .resource_mut::<EffectMergeRegistry>()
+            .register::<EffectStacks>(merge_effect_stacks);
+    }
+}
+
+/// Tracks the number stacks of a [merge effect](crate::EffectMode::Merge) that have been applied to an entity.
+#[derive(Component, Reflect, Eq, PartialEq, Ord, PartialOrd, Debug, Copy, Clone)]
+#[reflect(Component, Default, PartialEq, Debug, Clone)]
+pub struct EffectStacks(pub u8);
+
+impl Default for EffectStacks {
+    fn default() -> Self {
+        Self(1)
+    }
+}
+
+impl Deref for EffectStacks {
+    type Target = u8;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl DerefMut for EffectStacks {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+
+impl Add<u8> for EffectStacks {
+    type Output = Self;
+
+    fn add(self, rhs: u8) -> Self::Output {
+        Self(self.0 + rhs)
+    }
+}
+
+impl AddAssign<u8> for EffectStacks {
+    fn add_assign(&mut self, rhs: u8) {
+        self.0 += rhs
+    }
+}
+
+/// Merge logic for [`EffectStacks`].
+fn merge_effect_stacks(mut new: EntityWorldMut, outgoing: Entity) {
+    let outgoing = *new.world().get::<EffectStacks>(outgoing).unwrap();
+    *new.get_mut::<EffectStacks>().unwrap() += outgoing.0;
+}
diff --git a/src/timer.rs b/src/component/timer.rs
similarity index 99%
rename from src/timer.rs
rename to src/component/timer.rs
index dea46d5..f037da7 100644
--- a/src/timer.rs
+++ b/src/component/timer.rs
@@ -1,5 +1,5 @@
-use crate::ReflectComponent;
 use crate::registry::EffectMergeRegistry;
+use crate::ReflectComponent;
 use bevy_app::{App, Plugin, PreUpdate};
 use bevy_ecs::component::Mutable;
 use bevy_ecs::prelude::{Commands, Component, Entity, Query, Res};
@@ -9,7 +9,7 @@ use bevy_reflect::Reflect;
 use bevy_time::{Time, Timer, TimerMode};
 use std::time::Duration;
 
-pub(super) struct TimerPlugin;
+pub(crate) struct TimerPlugin;
 
 impl Plugin for TimerPlugin {
     fn build(&self, app: &mut App) {
diff --git a/src/lib.rs b/src/lib.rs
index 7ac1c06..aa13687 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -2,20 +2,20 @@
 
 mod bundle;
 mod command;
+mod component;
 mod registry;
 mod relation;
-mod timer;
 
 use bevy_app::{App, Plugin};
 use bevy_ecs::prelude::*;
-use bevy_reflect::Reflect;
 use bevy_reflect::prelude::ReflectDefault;
+use bevy_reflect::Reflect;
 
 pub use bundle::*;
 pub use command::*;
+pub use component::*;
 pub use registry::*;
 pub use relation::*;
-pub use timer::*;
 
 /// Setup required types and systems for `bevy_alchemy`.
 pub struct AlchemyPlugin;
@@ -29,7 +29,8 @@ impl Plugin for AlchemyPlugin {
             .register_type::<Delay>()
             .register_type::<TimerMergeMode>()
             .init_resource::<EffectMergeRegistry>()
-            .add_plugins(TimerPlugin);
+            .add_plugins(TimerPlugin)
+            .add_plugins(StackPlugin);
     }
 }