Ultrasonic manipulation has emerged as a simple and powerful tool for trapping, aggregation and separation of cells, in particular in micro-scaled systems. Traditionally, the technology has proven to be suitable for treatment of high-density cell and particle suspensions, where large cell and particle numbers are handled simultaneously. In this talk, we describe how ultrasound can be combined with microfluidics and microplates for particle and cell manipulation approaching the single-cell level. We demonstrate different cell handling methods with the purpose to select, trap, aggregate and position individual cells in micro-devices based on multi-frequency ultrasonic actuation, and we discuss applications of the technology involving immune cell interaction studies.