Geohot surprised everyone by releasing limera1n yesterday, a day before the release of greenpois0n by the Chronic Dev Team.

Limera1n can jailbreak iPhone 3GS, iPhone 4,  iPad, iPod Touch 3G  and the new iPod Touch 4G.

In this guide, we will take you through the step by step procedure to jailbreak iPhone 4 and iPhone 3GS.

Here are some important points to note before you proceed.

• This guide is only for iPhone 4 and iPhone 3GS users. iPod Touch 3G and iPod Touch 4G users can use this step by step guide to jailbreak their iPhone using limera1n. iPhone 3G and iPod Touch 2G users can use Redsn0w to jailbreak their iPod Touch.

• Please note that jailbreaking your iPhone may void your warranty and hence proceed with caution.

• Do not forget to backup your iPhone before you proceed. You can refer to this post for instructions on how to backup your iPhone.

• Limera1n supports iOS 4, iOS 4.0.1, iOS 4.0.2 and iOS 4.1.

• Limera1n is currently available for Windows, Geohot plans to release the Mac and Linux versions of limera1n soon.

• Please do NOT upgrade to iOS 4.1 if you want to unlock your iPhone. You should wait for iPhone Dev Team to release PwnageTool.

• Limera1n does NOT hactivate your iPhone, so your iPhone should be activated via iTunes first.

• After the jailbreaking process is complete, do not forget to checkout our article on tips to keep your iPhone secure.

• Please ensure you are running iTunes 9.2 or later.

Step 1: Download the latest version of limera1n from this link and save the application on your desktop.

Step 2: Double click on the limera1n exe to launch the application.

Step 3: Please ensure that your iPhone is connected to the computer.

Step 4: Click on the "make it rain” button.

Step 5: You will see that limera1n puts your iPhone in recovery mode. Immediately after this, follow the instructions.

Step 6: Limera1n will be prompt you to press both the home and power buttons.

Step 7: Limera1n will be then prompt you to release the Power button. Continue to press the home button.

Step 8: You will see that limera1n has put your iPhone in DFU mode. Continue to press the home button.

Step 9: While limera1n performs the exploit, you will see the limera1n logo on your iPhone.

Step 10: When limera1n has successfully jailbroken your iPhone, you will see “done” and get the following message.

Step 11: You need to restart your iPhone. You will notice that there is a new app called limera1n installed on your iPhone.

Step 12: Launch the limera1n app to install Cydia on your iPhone. Select Cydia and tap on the Install button to download and install it.

Step 13: After Cydia has been installed, reboot your iPhone.

Step 14: You should find Cydia on your iPhone’s homescreen. You can launch the limera1n app to uninstall it as it is no longer required.

Hope this helped. Please don't forget to drop us a line to tell us how it goes.