Targets with limited mass or volume (for example in the form of spherical targets with diameters of several µm only) are of supreme interest to ion acceleration for various reasons. The spatial limitation of the target confines the transmitted laser energy to a small volume for a much longer time, instead of allowing it to disperse laterally. This makes the generation of extremely high field strengths to accelerate the ions possible. On the other hand, choosing appropriate target materials can modify the density of the plasma which is generated by the high-intensity laser pulses, crucially determining the transfer of laser energy to the target. In collaboration with GSI Helmholtz Centre and the University of Frankfurt (Dr. Robert Grisenti and Dr. Paul Neumayer), spherical cryogenically-cooled H2, D2, He and Xe targets with diameters between 5 and 20 µm are produced and provided for subsequent interaction with the laser pulses. Apart from the detailed investigation of the ions’ acceleration, research focuses on the generation of warm dense matter.