If you are a Mac user with Thunderbolt or USB 3.0 but don't have SSD internal hard drive, then you must be unaware of the blazing data transfer and boot up speed that the SSDs provide. Even though, they are not just good for speed, there are dozens of other advantages that SSD have over HDD. We will get into that detail some other time. Well, here's the thing, you can simply boot from the external SSD without even opening the Mac. Though if you are not one who likes to carry around the extra things, then you can just head over to our tutorial, which will teach you about to replace the hard drive on your Macbook with an SSD. But if you are already done replacing the hard drive with an SSD, or either you are looking to upgrade your iMac or Mac mini, then we will guide you through the process of booting from external SSD & speed up your Mac. Now to begin, you have to first download the OS X version you are using. To do that, you have to head to the App Store (command+ space and type "app store" to find the application). Head over to the product page of the for the OS version you are using (in our case, we are on OS X 10.10.2). Click on the download, and then you would have to continue to download the Installer. We recommend that you don't turn off the computer after you have finished downloading the installer, as if you are not familiar with Mac's OS, the installer will be cleared as soon as you turn off the computer. Since the full installer is in gigabytes of size, you would have to wait for the next step to proceed (depends on your internet connection speed). It will have everything necessary to complete fresh installation of Mac OS. Even though, it would be a fresh installation, the Migration assistant on Mac allows you to transfer the applications, data, and all kinds of settings from your other Mac Hard Disk as well as from other Mac computer (which would be wirelessly). But that is for another tutorial. You would have to open the Disk Utility (command + space and type the name of the application) to further proceed with installation of the file, which includes the setting up of SSD for new Mac OS. Click on your new SSD and choose the partition tab, from the drop-down list, choose partition 1. You can either make different number of partition or break down the SSD storage in different drives, or you could choose to use the whole storage space in one partition and use the Hard Disk for your other storage needs. Select Mac OS Extended (Journaled) as the format and Name the new partition whatever you'd like. Click the Options button, which you'll see under partition layout, and choose the GUID partition table as the partition scheme, and then click OK. Make sure to verify your choices final time, and click Apply on the disk utility window if you want to commit the changes to a new disk. Now go ahead and start the OS X installation wizard, and continue through the first screens until you reach the disk selection step. There select show all disks, and choose the recently created SSD partition, finally select the "Install", and confirming the administrative password to begin installation of OS X on your new drive. If you are doing this process on an external hard disk, then you might want to restore the data via the Time Machine backup, for which you would have to shut down the Mac hold Command + R while booting it up again. You'll see the recovery options window and from here you can select "Restore from a Time Machine Backup", and follow the instructions to restore the files and preferences from the backup you to took earlier for your new install. Though, if you've installed a new SSD replacing your optical drive on your Mac, then you wouldn't need to go through the above procedure. You'll just have to open the installer file and follow the simple wizard instructions, remember to select your new SSD as the installation drive. The computer will reboot and would have to go through the installation steps, including setting up the Wi-Fi, transferring the application preferences from your Mac HD to SSD. The migration assistant will help you out and allow you to transfer the data and settings from various options including, Time Machine, Other Mac PC or others. After completing the installation process, you would like to choose the SSD drive as your default startup disk, which will allow computer to boot from the newly installed drive. To do that you have to go to, select Spotlight Search (Command + Space), their search for Startup Disk and open the application. Click the Apple icon in the top-left corner, and select the "System Preferences", and then "Startup Disk". Now choose your external SSD drive in the list and mark as the target disk mode. It will ask to restart the computer in target disk mode, once you do that, your Startup Disk would be changed to the SSD on which you newly installed the OS X.