diff --git a/SpecRunner.html b/SpecRunner.html
index 0265dc18..061b0e1b 100644
--- a/SpecRunner.html
+++ b/SpecRunner.html
@@ -16,8 +16,8 @@
     <script src="tests/chronometer.spec.js"></script>
 
     <!-- Bonus Iteration 9: Centiseconds -->
-    <!-- <script src="src/chronometer-centiseconds.js"></script> -->
-    <!-- <script src="tests/chronometer-centiseconds.spec.js"></script> -->
+    <script src="src/chronometer-centiseconds.js"></script>
+    <script src="tests/chronometer-centiseconds.spec.js"></script>
 
   </head>
 
diff --git a/index.html b/index.html
index 32e914c7..4b64407d 100644
--- a/index.html
+++ b/index.html
@@ -38,10 +38,10 @@ <h3>Splits</h3>
 
 
   <!--  Iterations 1 - 8 -->
-  <script src="src/chronometer.js"></script>
+  <!-- <script src="src/chronometer.js"></script> -->
 
   <!-- Bonus Iteration 9: Centiseconds -->
-  <!-- <script src="src/chronometer-centiseconds.js"></script> -->
+  <script src="src/chronometer-centiseconds.js"></script>
 
   
   <!--  DOM manipulation logic -->
diff --git a/src/chronometer-centiseconds.js b/src/chronometer-centiseconds.js
index 8337b5b6..c9bdd0db 100644
--- a/src/chronometer-centiseconds.js
+++ b/src/chronometer-centiseconds.js
@@ -1,37 +1,55 @@
 class Chronometer {
   constructor() {
     // ... your code goes here
+    this.currentTime = 0;
+    this.intervalId = null;
   }
 
   start(printTimeCallback) {
     // ... your code goes here
+    this.intervalId = setInterval(() =>{
+      this.currentTime += 10;
+      if (printTimeCallback) {
+        printTimeCallback();
+      }
+    }, 10);
   }
 
   getMinutes() {
     // ... your code goes here
+   return Math.floor(this.currentTime / 60000);
   }
 
   getSeconds() {
     // ... your code goes here
+    return Math.floor((this.currentTime / 1000)) % 60;
   }
 
   getCentiseconds() {
-    // ... your code goes here
+    return Math.floor((this.currentTime % 1000) / 10);
   }
 
   computeTwoDigitNumber(value) {
     // ... your code goes here
+    return value.toString().padStart(2 , "0");
   }
 
   stop() {
     // ... your code goes here
+    clearInterval(this.intervalId);
+    this.intervalId = null;
   }
 
   reset() {
     // ... your code goes here
+    clearInterval(this.intervalId);
+    this.currentTime = 0;
+    this.intervalId = null;
   }
 
   split() {
     // ... your code goes here
+    return `${this.computeTwoDigitNumber(this.getMinutes())}:${this.computeTwoDigitNumber(this.getSeconds())}:${this.computeTwoDigitNumber(this.getCentiseconds())}`;
   }
 }
+
diff --git a/src/chronometer.js b/src/chronometer.js
index 83c75bd2..aa5a2b25 100644
--- a/src/chronometer.js
+++ b/src/chronometer.js
@@ -1,33 +1,47 @@
 class Chronometer {
   constructor() {
     // ... your code goes here
+    this.currentTime = 0;
+    this.intervalId = null;
   }
 
   start(printTimeCallback) {
     // ... your code goes here
+    this.intervalId = setInterval(() =>{
+      this.currentTime++;
+      if (printTimeCallback != null) {
+        printTimeCallback();
+      }
+    }, 1000);
   }
 
   getMinutes() {
     // ... your code goes here
+   return parseInt(Math.floor(this.currentTime / 60));
   }
 
   getSeconds() {
     // ... your code goes here
+    return this.currentTime % 60;
   }
 
   computeTwoDigitNumber(value) {
     // ... your code goes here
+    return value.toString().padStart(2 , "0");
   }
 
   stop() {
     // ... your code goes here
+    clearInterval(this.intervalId);
   }
 
   reset() {
     // ... your code goes here
+    this.currentTime = 0;
   }
 
   split() {
     // ... your code goes here
+    return `${this.computeTwoDigitNumber(this.getMinutes())}:${this.computeTwoDigitNumber(this.getSeconds())}`;
   }
 }