Over the past decades we witnessed a tremendous shift in the principles of architectural design based on the advancement of computer aided design and manufacturing. Computation in architecture came with a whole new set of techniques as well as theories that did change the way we build and design today. This research investigates ways to embed computational simulation and optimisation into architectural design processes at an early, conceptual stage. Simulation and optimization are not seen as a post-design strategy to improve performance aspects of a well-developed design, but rather as design strategies in their own rights. Therefore, design approaches employing simulation and optimization were developed, tested and discussed. Conditions and prerequisites for successfully embedding simulation and optimization into architectural design processes were formulated and benefits were derived. Design approaches that use digital simulation and optimization are characterised by not favouring rational form finding above intuitive form making, or vice versa – they rather support informed design decisions. Therefore, Informed Form Generation is established as a design approach within this thesis. It is not one specific, universally applicable process, but rather comprises a category of approaches and constitutes an attitude.