The prior research on product platforms has added to our knowledge from a strategic, technological, and organizational point of view. However, the existing literature, while exploring the platform concept, considers the actual development of platforms from a rather general perspective although companies develop platforms for different aims, purposes, and product scopes. Following on from this, the requirements for platform development resources, the ways of organizing platform development, and the implications for management styles have not been explored and are presumably varying. To start elaborating on this, the research behind this article uses a clinical research approach in seven platform development cases from eight years' longitudinal research in three global manufacturing automotive original equipment manufacturers. Platform development is here defined and treated as development with the aim of creating a foundation, the platform, for the subsequent development of derivative products. The analysis of the development of platform in different strategic situations and with different purposes demonstrates how combinations of changes in components and/or architecture represent a key differentiator. An important result is the advancement of the platform perspective from an architecture with a set of components to a classification of four platform development variants based on alternative changes in architecture and/or components. Each type has different complexities and characteristics influencing the project length, requirements for platform development resources, principles for organizing, and implications for management styles.