In this lesson, the student will learn about CloudFormation Custom Resources. CloudFormation Custom Resources enable you to write custom provisioning logic in templates that AWS CloudFormation runs anytime you create, update, or delete stacks. The most common use for custom resources is to have a Lambda Function which executes and returns specific results back to CloudFormation during stack creation. This lesson will take an in-depth look at a Lambda backed custom resource and all of the components needed for execution. The lesson will end will a walkthrough using a Lambda backed custom resource to verify a password.