Just-In-Time (JIT) provisioning is a user provisioning strategy that leverages Security Assertion Markup Language (SAML) to create user accounts on-the-fly, allowing employees to sign in to an app with SSO even if they haven't been pre-approved by their IT department. JIT offers convenience and adoption benefits for both startups and customers, as it eliminates the need for manual account creation or approval processes. It is a secure way to onboard users, as only authorized and verified employees can access their email accounts. The main difference between JIT and SCIM provisioning lies in approval and timing; while JIT provisions accounts instantly during login, SCIM allows for more control over account provisioning but requires manual action or an automated system tied into the customer's IdP.