diff --git a/src/Co.cs b/src/Co.cs
index 9909111..d888ce5 100644
--- a/src/Co.cs
+++ b/src/Co.cs
@@ -25,8 +25,12 @@ private static Coroutine[] GetCoroutines(IEnumerator[] enumerators)
         return coroutines;
     }
 
+    
     public static float DeltaTime => CoroutineManager.Instance.DeltaTime;
     public static double DeltaTimeDouble => CoroutineManager.Instance.DeltaTimeDouble;
+    
+    public static float PhysicsDeltaTime => CoroutineManager.Instance.PhysicsDeltaTime;
+    public static double PhysicsDeltaTimeDouble => CoroutineManager.Instance.PhysicsDeltaTimeDouble;
 
 
     public static void Run(CoroutineBase coroutine)
diff --git a/src/CoProcessMode.cs b/src/CoProcessMode.cs
new file mode 100644
index 0000000..fb01b90
--- /dev/null
+++ b/src/CoProcessMode.cs
@@ -0,0 +1,21 @@
+namespace HCoroutines;
+
+/// <summary>
+/// The ProcessMode determines when the Update() method of a coroutine is called.
+/// </summary>
+public enum CoProcessMode {
+    /// <summary>
+    /// The ProcessMode is inherited from the parent coroutine. If there is no parent, then the Normal mode is used.
+    /// </summary>
+    Inherit, 
+    
+    /// <summary>
+    /// The Update() method is called during each process frame (like the _Process() method).
+    /// </summary>
+    Normal, 
+    
+    /// <summary>
+    /// The Update() method is called during each physics frame (like the _PhysicsProcess() method).
+    /// </summary>
+    Physics
+}
\ No newline at end of file
diff --git a/src/CoroutineBase.cs b/src/CoroutineBase.cs
index e99f724..07c136b 100644
--- a/src/CoroutineBase.cs
+++ b/src/CoroutineBase.cs
@@ -20,6 +20,9 @@ public class CoroutineBase
     public bool IsAlive = true;
     public bool IsPlaying = false;
 
+    // TODO: Add way to set this property.
+    public CoProcessMode ProcessMode { get; private set; }
+
     public void StartCoroutine(CoroutineBase coroutine)
     {
         coroutine.Manager = Manager;
@@ -34,7 +37,10 @@ public void StartCoroutine(CoroutineBase coroutine)
     /// </summary>
     public virtual void OnEnter()
     {
-        ResumeUpdates();
+        if (this.ProcessMode == CoProcessMode.Inherit) 
+        {
+            this.ProcessMode = Parent?.ProcessMode ?? CoProcessMode.Normal;
+        }    
     }
 
     /// <summary>
diff --git a/src/CoroutineManager.cs b/src/CoroutineManager.cs
index f656a19..e915f0c 100644
--- a/src/CoroutineManager.cs
+++ b/src/CoroutineManager.cs
@@ -1,20 +1,22 @@
 using Godot;
 using System;
-using System.Collections.Generic;
+using HCoroutines.Util;
 
 namespace HCoroutines;
 
 public partial class CoroutineManager : Node
 {
     public static CoroutineManager Instance { get; private set; }
+    
     public float DeltaTime { get; private set; }
     public double DeltaTimeDouble { get; private set; }
+    
+    public float PhysicsDeltaTime { get; private set; }
+    public double PhysicsDeltaTimeDouble { get; private set; }
 
-    private bool isIteratingActiveCoroutines = false;
-    private HashSet<CoroutineBase> activeCoroutines = new();
-    private HashSet<CoroutineBase> coroutinesToDeactivate = new();
-    private HashSet<CoroutineBase> coroutinesToActivate = new();
-
+    private DeferredHashSet<CoroutineBase> activeProcessCoroutines = new();
+    private DeferredHashSet<CoroutineBase> activePhysicsProcessCoroutines = new();
+    
     public void StartCoroutine(CoroutineBase coroutine)
     {
         coroutine.Manager = this;
@@ -23,27 +25,31 @@ public void StartCoroutine(CoroutineBase coroutine)
 
     public void ActivateCoroutine(CoroutineBase coroutine)
     {
-        if (isIteratingActiveCoroutines)
-        {
-            coroutinesToActivate.Add(coroutine);
-            coroutinesToDeactivate.Remove(coroutine);
-        }
-        else
+        switch (coroutine.ProcessMode)
         {
-            activeCoroutines.Add(coroutine);
+            case CoProcessMode.Normal: 
+            case CoProcessMode.Inherit:
+                activeProcessCoroutines.Add(coroutine);
+                break;
+            
+            case CoProcessMode.Physics:
+                activePhysicsProcessCoroutines.Add(coroutine);
+                break;
         }
     }
 
     public void DeactivateCoroutine(CoroutineBase coroutine)
     {
-        if (isIteratingActiveCoroutines)
-        {
-            coroutinesToDeactivate.Add(coroutine);
-            coroutinesToActivate.Remove(coroutine);
-        }
-        else
+        switch (coroutine.ProcessMode)
         {
-            activeCoroutines.Remove(coroutine);
+            case CoProcessMode.Normal: 
+            case CoProcessMode.Inherit:
+                activeProcessCoroutines.Remove(coroutine);
+                break;
+            
+            case CoProcessMode.Physics:
+                activePhysicsProcessCoroutines.Remove(coroutine);
+                break;
         }
     }
 
@@ -57,9 +63,22 @@ public override void _Process(double delta)
         DeltaTime = (float)delta;
         DeltaTimeDouble = delta;
 
-        isIteratingActiveCoroutines = true;
+        UpdateCoroutines(activeProcessCoroutines);
+    }
+
+    public override void _PhysicsProcess(double delta)
+    {
+        PhysicsDeltaTime = (float)delta;
+        PhysicsDeltaTimeDouble = delta;
+
+        UpdateCoroutines(activePhysicsProcessCoroutines);
+    }
+
+    private void UpdateCoroutines(DeferredHashSet<CoroutineBase> coroutines)
+    {
+        coroutines.Lock();
 
-        foreach (CoroutineBase coroutine in activeCoroutines)
+        foreach (CoroutineBase coroutine in coroutines.Items)
         {
             if (coroutine.IsAlive && coroutine.IsPlaying)
             {
@@ -74,18 +93,6 @@ public override void _Process(double delta)
             }
         }
 
-        isIteratingActiveCoroutines = false;
-
-        foreach (CoroutineBase coroutine in coroutinesToActivate)
-        {
-            activeCoroutines.Add(coroutine);
-        }
-        coroutinesToActivate.Clear();
-
-        foreach (CoroutineBase coroutine in coroutinesToDeactivate)
-        {
-            activeCoroutines.Remove(coroutine);
-        }
-        coroutinesToDeactivate.Clear();
+        coroutines.Unlock();
     }
 }
\ No newline at end of file
diff --git a/src/Util/DeferredHashSet.cs b/src/Util/DeferredHashSet.cs
new file mode 100644
index 0000000..20fd20d
--- /dev/null
+++ b/src/Util/DeferredHashSet.cs
@@ -0,0 +1,67 @@
+using System.Collections.Generic;
+
+namespace HCoroutines.Util;
+
+/// <summary>
+/// HashSet implementation that defers Add() and Remove() calls during iteration.
+/// </summary>
+public class DeferredHashSet<T>
+{
+    public HashSet<T> Items = new();
+    
+    private bool isIterating = false;
+    private HashSet<T> itemsToAdd = new();
+    private HashSet<T> itemsToRemove = new();
+
+    public void Add(T item)
+    {
+        if (isIterating)
+        {
+            itemsToAdd.Add(item);
+            itemsToRemove.Remove(item);
+        }
+        else
+        {
+            Items.Add(item);
+        }
+    }
+
+    public void Remove(T item)
+    {
+        if (isIterating)
+        {
+            itemsToRemove.Add(item);
+            itemsToAdd.Remove(item);
+        }
+        else
+        {
+            Items.Remove(item);
+        }
+    }
+
+    public void Lock()
+    {
+        isIterating = true;
+    }
+
+    public void Unlock()
+    {
+        isIterating = false;
+        ExecutePendingAddRemoves();
+    }
+
+    private void ExecutePendingAddRemoves()
+    {
+        foreach (T item in itemsToAdd)
+        {
+            Items.Add(item);
+        }
+        itemsToAdd.Clear();
+
+        foreach (T item in itemsToRemove)
+        {
+            Items.Remove(item);
+        }
+        itemsToRemove.Clear();
+    }
+}
\ No newline at end of file