  Thermal expansion and magnetostriction are directional dependent
thermodynamic quantities. For the characterization of novel quantum phases of
matter it is required to study materials under multi-extreme conditions, in
particular down to very low temperatures, in very high magnetic fields, as well
as under high pressure. We developed a miniaturized capacitive dilatometer
suitable for temperatures down to 20 mK and usage in high magnetic fields,
which exerts a large spring force between 40 to 75 N on the sample. This
corresponds to a uniaxial stress up to 3 kbar for a sample with cross-section
of (0.5~mm)$^2$. We describe the design and performance test of the dilatometer
which resolves length changes with high resolution of $0.02 \mathrm{\AA}$ at
low temperatures. The miniaturized device can be utilized in any standard
cryostat, including dilution refrigerators or the commercial physical property
measurement system.
