In this paper, we present the experimental implementation for a concept for the construction of inhomogeneous phantoms for imaging in diffuse media based on totally absorbing objects that was proposed in the previous companion paper.1 This work stems from the outcome of a large collaboration among seven institutions from four countries within the framework of the European nEUROPt Project that put great emphasis on standardization approaches to assess the performance of noninvasive optical brain imagers. The key motivation for these activities is that, while the investigation of the human body by diffusely propagated light has brought a wealth of different techniques and applications2 (e.g., optical mammography,3–5 neoadjuvant chemotherapy monitoring,6 breast cancer risk assessment,7 brain functional imaging,2,8,9 neuromonitoring,10 muscle oximetry,11 study of epilepsy,12,13 investigation of bone and joint pathologies,14 and photodynamic therapy dosimetry15), there is still a compelling need for standardization and quality assessment of instruments to bring the whole field to a clinically mature stage.16 Indeed, the large variety of techniques and instruments addressing diverse clinical problems demand some clearly identified and shared procedures to test and validate the optical systems. Common standardization tools help in comparing results obtained in different clinical studies, permit one to grade different instruments’ performances or subsequent upgrades of the same system, and address the research—particularly at the industrial level—toward those parameters that best match the clinical needs. This process necessarily passes through the proposition of good reproducible and reliable phantoms and procedures, the buildup of a widespread consensus in the scientific community and, at last, the adoption of good laboratory practices and formalization by standardization bodies. Clearly, the availability of well characterized, reliable, reproducible, and realistic phantoms is essential for this process. Concerning homogeneous phantoms, the status is quite advanced, with many tested options,17–24 off-the-shelf solid phantoms with well characterized and documented optical properties,25 and good agreement in liquid phantoms’ characterization in multilaboratory studies.26 Conversely, the situation of inhomogeneous phantoms is less consolidated due to many criticalities and large combinations of geometries and optical properties. Different approaches have been proposed. Without claiming to give a comprehensive review of the whole field here—more information can be gathered in the review papers24,27 and a recent special issue of Biomed. Opt. Express16—we just recall that three schemes can be adopted for this purpose, namely liquid–liquid,28 liquid–solid,29–31 and solid–solid32–34 structures, each of them with different advantages and criticalities. Liquid–liquid phantoms realize inhomogeneous properties by embedding a liquid solution (typically based on intralipid and ink) in a small cell—made of glass, thin plastic, or latex—suspended within another homogeneous solution. The advantages are the great flexibility and the reliability in the choice of optical properties, the possibility to move the inclusion within the medium, and also to realize a purely homogeneous reference state. Conversely, the main concerns are the possible light guiding effects in the small cell walls, the challenging fabrication and the exact placement of soft-flexible objects, the great perturbation produced by transparent walls in the measurement tank for reflectance measurements,35 and generally the complex handling procedures in routine clinical settings. The liquid–solid approach replaces the liquid perturbation with a solid one crafted from a solid phantom or from a liquid phantom solidified with the addition of a hardener, e.g., agar32 or polyacrylamide.31 In this case, the handling and the replacement of the perturbation is easier, and light-guiding effects are avoided. On the other hand, the exact matching of optical properties is not trivial due to the application of two-different phantom recipes, the fact that the hardener may change the inclusion properties,32 and the refractive index mismatch between the solid inclusion and its surroundings has to be considered. Solid–solid structures are definitely the best solution for routine use in clinics and also as a fast and reliable option in the laboratory. Yet, the fabrication of such phantoms is not straightforward. It is not possible to replace or move the perturbation, and it is not trivial to precisely measure the optical properties of the inclusion. Among this class, one can also mention electrically activated phantoms where a local increase in the absorption properties is produced by localized heating of targets impregnated with thermochromic pigment33 or liquid-crystal–based dynamic phantom for quality assurance of functional near-infrared spectroscopy devices.36 Dynamic changes can be easily achieved with such a rugged solid phantom, yet exact control and reproducibility are still an issue.