+++
title = "6.3 Perform the Experiment"
chapter = true
weight = 20
+++

# Perform the Experiment

Now that we've defined our experiment and gathered observations, let's run the experiment. Start by opening the [Gremlin](https://app.gremlin.com) tab in your browser. On the left navigation bar, click **Attacks**, followed by **New Attack.** 

![Gremlin UI New Attack](/images/gremlin/gremlin_ui_create_new_attack.png)

Under **"What do you want to attack?"**, select **Infrastructure**, then **Hosts**. You can either select each host individually, or click **Target all hosts** to select all three of your hosts.

![Gremlin UI Select Hosts](/images/gremlin/gremlin_ui_select_hosts.png)

Expand **Choose a Gremlin** and select **Resource**, then **CPU**. Change **Length** to `360`, change **CPU Capacity** to `80` and select **"All Cores"** from the dropdown. 


![Gremlin UI CPU Attack](/images/gremlin/gremlin_ui_cpu_attack.png)

Now, click **Unleash Gremlin** to start the attack.

{{% notice tip %}}
If you want to stop the attack at any time, click either the **Halt** or **Halt All Attacks** button in the top-right corner.
{{% /notice %}}

🎉 Congrats, you've unleashed your first attack! In the next page, we will talk about observing the chaos engineering experiment we just unleashed.