Finally, the materials were injection moulded into their final shape using a BOY XS micro injection moulding machine. The process for PLA and PLA with 20% HAp composites was carried out with a barrel temperature of 180 °C, a flow channel temperature of 170 °C, an injection pressure of 240 bar, a cooling time of 15 s and a cooling temperature of 50 °C. For PLA composites with 40% HAp, only the temperatures were adjusted, set at 190 °C in the barrel and 180 °C in the flow channels. For PCL-based materials, the cooling parameters were changed to a mould temperature of 40 °C and a cooling time of 40 s, while the process temperatures were set to 120 °C and 110 °C respectively. During the injection moulding process, three types of test specimens were produced for each material: 1) dumbbell-type 5A specimens according to ISO 527, 2) bars with dimensions of 80 mm × 10 mm × 4 mm, and 3) plates with dimensions of 35 mm × 35 mm × 2 mm. Morphology and elemental composition of the composites were characterized and/or verified by scanning electron microscopy (SEM) using a microscope MAIA3 (Tescan, Brno, Czech Republic) equipped with an X-MaxN 20 detector for energy-dispersive spectroscopy (EDX, Oxford Instruments, Abingdon, UK). All samples were fixed on a metallic support with a conductive carbon tape, sputter-coated with a thin platinum layer (vacuum sputter coater SCD 050; Leica, Austria; thickness of the Pt layer: approx. 4 nm) observed by means of secondary electron imaging (SEM/SE) at accelerating voltage 3 kV or by means of back scattered electron imaging (SEM/BSE) at accelerating voltage 10kV. The EDX spectra (elemental microanalysis) were collected at an increased accelerating voltage of 30 kV. Three types of samples were prepared and studied: (i) filler particles deposited on a conductive support, (ii) smooth cut surfaces and (iii) fracture surfaces. (i) The filler particles (nHAP or μHAP) were just deposited onto the sticky surface of double-adhesive carbon tape on a microscopic stub. (ii) Smooth cut surfaces were prepared both parallel and perpendicular to the injection molding direction. The samples were pre-cut with a hand saw and the final smooth surfaces were cut with a rotary microtome RM2255 (Leica, Austria) at room temperature using a freshly-prepared glass knife. (iii) Fracture surfaces were obtained by tensile testing. The fractures were imaged as they appeared after the specimen broke.