This review covers recent advancements in particle engineering via spray drying, highlighting the shift from empirical methods to an engineering approach based on a better understanding of particle formation. Microparticles with nanoscale substructures can now be designed, enhancing stability and efficacy in pharmaceutical applications. The review provides a theoretical framework for particle design calculations and discusses experimental research into parameters influencing particle formation. A classification based on dimensionless numbers is presented to estimate how excipient properties and process parameters affect particle morphology. Various pharmaceutical applications, including low-density particles, composite particles, microencapsulation, and glass stabilization, are discussed, emphasizing the underlying particle formation mechanisms and design concepts. The introduction explains the evolution of microparticles from simple carriers to complex dosage forms with specific functions, such as stabilization, transport, and targeting. Particle engineering combines elements of microbiology, chemistry, and other sciences to design structured microparticles rationally. The review focuses on spray drying, with an emphasis on recent literature, and discusses the challenges and advancements in understanding and controlling particle formation processes. The terminology of structured microparticles is clarified, defining terms like core, shell, and coat, and describing various morphologies, including layered structures, solid foams, and composite shells. The review also covers particle size, distribution of components, and the role of dimensionless numbers in predicting particle properties. Experimental techniques for studying droplet drying and particle formation are reviewed, including single droplet levitation, Leidenfrost phenomena, and droplet chains. The formation mechanisms are categorized into low and high Peclet numbers, with detailed explanations of how surface activity and evaporation rates influence particle morphology. Application examples, such as density control and solid foam particles, are discussed. Low-density particles are advantageous for pulmonary drug delivery, and specific formulations like Large Porous Particles and PulmoSpheres™ are highlighted for their performance in DPIs and pulmonary delivery systems.This review covers recent advancements in particle engineering via spray drying, highlighting the shift from empirical methods to an engineering approach based on a better understanding of particle formation. Microparticles with nanoscale substructures can now be designed, enhancing stability and efficacy in pharmaceutical applications. The review provides a theoretical framework for particle design calculations and discusses experimental research into parameters influencing particle formation. A classification based on dimensionless numbers is presented to estimate how excipient properties and process parameters affect particle morphology. Various pharmaceutical applications, including low-density particles, composite particles, microencapsulation, and glass stabilization, are discussed, emphasizing the underlying particle formation mechanisms and design concepts. The introduction explains the evolution of microparticles from simple carriers to complex dosage forms with specific functions, such as stabilization, transport, and targeting. Particle engineering combines elements of microbiology, chemistry, and other sciences to design structured microparticles rationally. The review focuses on spray drying, with an emphasis on recent literature, and discusses the challenges and advancements in understanding and controlling particle formation processes. The terminology of structured microparticles is clarified, defining terms like core, shell, and coat, and describing various morphologies, including layered structures, solid foams, and composite shells. The review also covers particle size, distribution of components, and the role of dimensionless numbers in predicting particle properties. Experimental techniques for studying droplet drying and particle formation are reviewed, including single droplet levitation, Leidenfrost phenomena, and droplet chains. The formation mechanisms are categorized into low and high Peclet numbers, with detailed explanations of how surface activity and evaporation rates influence particle morphology. Application examples, such as density control and solid foam particles, are discussed. Low-density particles are advantageous for pulmonary drug delivery, and specific formulations like Large Porous Particles and PulmoSpheres™ are highlighted for their performance in DPIs and pulmonary delivery systems.