diff --git a/src/components/menu/items/breathing-exercise.tsx b/src/components/menu/items/breathing-exercise.tsx
new file mode 100644
index 0000000..6d5dce4
--- /dev/null
+++ b/src/components/menu/items/breathing-exercise.tsx
@@ -0,0 +1,18 @@
+import { MdOutlineTimer } from 'react-icons/md/index';
+
+import { Item } from '../item';
+
+interface BreathingExerciseProps {
+  open: () => void;
+}
+
+export function BreathingExercise({ open }: BreathingExerciseProps) {
+  return (
+    <Item
+      icon={<MdOutlineTimer />}
+      label="Breathing Exercise"
+      shortcut="Shift + B"
+      onClick={open}
+    />
+  );
+}
diff --git a/src/components/menu/items/index.ts b/src/components/menu/items/index.ts
index e5c2904..08aa347 100644
--- a/src/components/menu/items/index.ts
+++ b/src/components/menu/items/index.ts
@@ -8,3 +8,4 @@ export { Presets as PresetsItem } from './presets';
 export { Shortcuts as ShortcutsItem } from './shortcuts';
 export { SleepTimer as SleepTimerItem } from './sleep-timer';
 export { CountdownTimer as CountdownTimerItem } from './countdown-timer';
+export { BreathingExercise as BreathingExerciseItem } from './breathing-exercise';
diff --git a/src/components/menu/menu.tsx b/src/components/menu/menu.tsx
index 52f8f6e..2692861 100644
--- a/src/components/menu/menu.tsx
+++ b/src/components/menu/menu.tsx
@@ -15,13 +15,19 @@ import {
   PresetsItem,
   ShortcutsItem,
   SleepTimerItem,
+  BreathingExerciseItem,
 } from './items';
 import { Divider } from './divider';
 import { ShareLinkModal } from '@/components/modals/share-link';
 import { PresetsModal } from '@/components/modals/presets';
 import { ShortcutsModal } from '@/components/modals/shortcuts';
 import { SleepTimerModal } from '@/components/modals/sleep-timer';
-import { Notepad, Pomodoro, CountdownTimer } from '@/components/toolbox';
+import {
+  Notepad,
+  Pomodoro,
+  CountdownTimer,
+  BreathingExercise,
+} from '@/components/toolbox';
 import { fade, mix, slideY } from '@/lib/motion';
 import { useSoundStore } from '@/stores/sound';
 
@@ -36,6 +42,7 @@ export function Menu() {
 
   const initial = useMemo(
     () => ({
+      breathingExercise: false,
       countdownTimer: false,
       notepad: false,
       pomodoro: false,
@@ -113,6 +120,9 @@ export function Menu() {
                     <Divider />
                     <PomodoroItem open={() => open('pomodoro')} />
                     <NotepadItem open={() => open('notepad')} />
+                    <BreathingExerciseItem
+                      open={() => open('breathingExercise')}
+                    />
                     <CountdownTimerItem open={() => open('countdownTimer')} />
 
                     <Divider />
@@ -144,6 +154,10 @@ export function Menu() {
         show={modals.pomodoro}
         onClose={() => close('pomodoro')}
       />
+      <BreathingExercise
+        show={modals.breathingExercise}
+        onClose={() => close('breathingExercise')}
+      />
       <CountdownTimer
         show={modals.countdownTimer}
         onClose={() => close('countdownTimer')}
diff --git a/src/components/toolbox/breathing/breathing.module.css b/src/components/toolbox/breathing/breathing.module.css
new file mode 100644
index 0000000..fdbd99d
--- /dev/null
+++ b/src/components/toolbox/breathing/breathing.module.css
@@ -0,0 +1 @@
+/* WIP */
diff --git a/src/components/toolbox/breathing/breathing.tsx b/src/components/toolbox/breathing/breathing.tsx
new file mode 100644
index 0000000..c807a22
--- /dev/null
+++ b/src/components/toolbox/breathing/breathing.tsx
@@ -0,0 +1,18 @@
+import { Modal } from '@/components/modal';
+import { Exercise } from './exercise';
+
+import styles from './breathing.module.css';
+
+interface TimerProps {
+  onClose: () => void;
+  show: boolean;
+}
+
+export function BreathingExercise({ onClose, show }: TimerProps) {
+  return (
+    <Modal show={show} onClose={onClose}>
+      <h2 className={styles.title}>Breathing Exercise</h2>
+      <Exercise />
+    </Modal>
+  );
+}
diff --git a/src/components/toolbox/breathing/exercise/exercise.module.css b/src/components/toolbox/breathing/exercise/exercise.module.css
new file mode 100644
index 0000000..0bfd464
--- /dev/null
+++ b/src/components/toolbox/breathing/exercise/exercise.module.css
@@ -0,0 +1,44 @@
+.exercise {
+  position: relative;
+  z-index: 1;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 75px 0;
+  margin-top: 12px;
+  background-color: var(--color-neutral-50);
+  border: 1px solid var(--color-neutral-200);
+  border-radius: 8px;
+
+  & .phase {
+    font-family: var(--font-display);
+    font-size: var(--font-lg);
+    font-weight: 600;
+  }
+
+  & .circle {
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    z-index: -1;
+    height: 55%;
+    aspect-ratio: 1 / 1;
+    background-image: radial-gradient(transparent, var(--color-neutral-100));
+    border: 1px solid var(--color-neutral-200);
+    border-radius: 50%;
+    transform: translate(-50%, -50%);
+  }
+}
+
+.selectBox {
+  width: 100%;
+  min-width: 0;
+  height: 45px;
+  padding: 0 12px;
+  margin-top: 8px;
+  font-size: var(--font-sm);
+  color: var(--color-foreground);
+  background-color: var(--color-neutral-100);
+  border: 1px solid var(--color-neutral-200);
+  border-radius: 8px;
+}
diff --git a/src/components/toolbox/breathing/exercise/exercise.tsx b/src/components/toolbox/breathing/exercise/exercise.tsx
new file mode 100644
index 0000000..da06512
--- /dev/null
+++ b/src/components/toolbox/breathing/exercise/exercise.tsx
@@ -0,0 +1,120 @@
+import { useState, useEffect } from 'react';
+import { motion } from 'framer-motion';
+
+import styles from './exercise.module.css';
+
+type Exercise = 'Box Breathing' | 'Resonant Breathing' | '4-7-8 Breathing';
+type Phase = 'inhale' | 'exhale' | 'holdInhale' | 'holdExhale';
+
+export function Exercise() {
+  const [selectedExercise, setSelectedExercise] =
+    useState<Exercise>('4-7-8 Breathing');
+
+  const getAnimationPhases = (
+    exercise: Exercise,
+  ): Array<'inhale' | 'holdInhale' | 'exhale' | 'holdExhale'> => {
+    switch (exercise) {
+      case 'Box Breathing':
+        return ['inhale', 'holdInhale', 'exhale', 'holdExhale'];
+      case 'Resonant Breathing':
+        return ['inhale', 'exhale'];
+      case '4-7-8 Breathing':
+        return ['inhale', 'holdInhale', 'exhale'];
+      default:
+        return ['inhale', 'holdInhale', 'exhale', 'holdExhale'];
+    }
+  };
+
+  const getAnimationDurations = (exercise: Exercise) => {
+    switch (exercise) {
+      case 'Box Breathing':
+        return { exhale: 4, holdExhale: 4, holdInhale: 4, inhale: 4 };
+      case 'Resonant Breathing':
+        return { exhale: 5, inhale: 5 };
+      case '4-7-8 Breathing':
+        return { exhale: 8, holdInhale: 7, inhale: 4 };
+      default:
+        return { exhale: 4, holdExhale: 4, holdInhale: 4, inhale: 4 };
+    }
+  };
+
+  const getLabel = (phase: Phase) => {
+    switch (phase) {
+      case 'inhale':
+        return 'Inhale';
+      case 'exhale':
+        return 'Exhale';
+      default:
+        return 'Hold';
+    }
+  };
+
+  const [phase, setPhase] = useState<Phase>('inhale');
+  const [durations, setDurations] = useState(
+    getAnimationDurations(selectedExercise),
+  );
+
+  const animationVariants = {
+    exhale: { scale: 1, transition: { duration: durations.exhale } },
+    holdExhale: {
+      scale: 1,
+      transition: { duration: durations.holdExhale || 4 },
+    },
+    holdInhale: {
+      scale: 1.5,
+      transition: { duration: durations.holdInhale || 4 },
+    },
+    inhale: { scale: 1.5, transition: { duration: durations.inhale } },
+  };
+
+  useEffect(() => {
+    setDurations(getAnimationDurations(selectedExercise));
+  }, [selectedExercise]);
+
+  useEffect(() => {
+    const phases = getAnimationPhases(selectedExercise);
+
+    let phaseIndex = 0;
+
+    setPhase(phases[phaseIndex]);
+
+    const interval = setInterval(
+      () => {
+        phaseIndex = (phaseIndex + 1) % phases.length;
+
+        setPhase(phases[phaseIndex]);
+      },
+      (durations[phases[phaseIndex]] || 4) * 1000,
+    );
+
+    return () => clearInterval(interval);
+  }, [selectedExercise, durations]);
+
+  return (
+    <>
+      <div className={styles.exercise}>
+        <motion.div
+          animate={phase}
+          className={styles.circle}
+          key={selectedExercise}
+          transition={{ ease: 'linear' }}
+          variants={animationVariants}
+          transformTemplate={(_, generatedString) =>
+            `translate(-50%, -50%) ${generatedString}`
+          }
+        />
+        <p className={styles.phase}>{getLabel(phase)}</p>
+      </div>
+
+      <select
+        className={styles.selectBox}
+        value={selectedExercise}
+        onChange={e => setSelectedExercise(e.target.value as Exercise)}
+      >
+        <option value="Box Breathing">Box Breathing</option>
+        <option value="Resonant Breathing">Resonant Breathing</option>
+        <option value="4-7-8 Breathing">4-7-8 Breathing</option>
+      </select>
+    </>
+  );
+}
diff --git a/src/components/toolbox/breathing/exercise/index.ts b/src/components/toolbox/breathing/exercise/index.ts
new file mode 100644
index 0000000..881062d
--- /dev/null
+++ b/src/components/toolbox/breathing/exercise/index.ts
@@ -0,0 +1 @@
+export { Exercise } from './exercise';
diff --git a/src/components/toolbox/breathing/index.ts b/src/components/toolbox/breathing/index.ts
new file mode 100644
index 0000000..323b544
--- /dev/null
+++ b/src/components/toolbox/breathing/index.ts
@@ -0,0 +1 @@
+export { BreathingExercise } from './breathing';
diff --git a/src/components/toolbox/index.ts b/src/components/toolbox/index.ts
index 67924b9..f8725ad 100644
--- a/src/components/toolbox/index.ts
+++ b/src/components/toolbox/index.ts
@@ -1,3 +1,4 @@
 export { Notepad } from './notepad';
 export { Pomodoro } from './pomodoro';
 export { CountdownTimer } from './countdown-timer';
+export { BreathingExercise } from './breathing';