Elastomers are a class of polymeric materials known for their viscoelasticity, low stiffness and high failure strain. In recent years, with the evolution of 3D printing and additive manufacturing technologies, macro-and microscale 3D printing of elastomers has drawn significant attention in academia and industrial settings. 3D printing of mechanically soft materials has found a wide range of applications across industries from automotive and wearable electronics to healthcare and soft robotics. For all of these applications, the mechanical characterization of the 3D printed elastomers is fundamental for understanding their interaction with the environment and is a key element in establishing structure-property relationships. While mechanical characterization of rigid materials such as metals is relatively straightforward and standardized measurement methods exist, the evaluation of mechanical properties of 3D printed elastomers presents unique challenges that increase as the size of the 3D printed structures decreases. First, almost all classes of materials exhibit a so-called 'size effect', where their properties vary when scaled down to micrometer and nanometer size, making it unreliable to extrapolate measurements obtained with macroscopic samples. Furthermore, the characterization of mechanical properties on the microscale requires specialized and often expensive microscopy-based equipment with high spatial resolution such as microscale compression setups, AFM, optical tweezers or by using nanoindentation. Nanoindentation is a microscale contact mechanics method that uses a hard indenter probe tip with known and well-characterized mechanical properties (often made of diamond) to deform a sample surface of unknown properties. It has gained popularity in the last two decades for characterizing mechanical properties at the microscale for rigid materials , but also for soft and biological samples, due to its ability to measure samples with limited dimensions and its sensitivity to sample anisotropy and inhomogeneity. In their tutorial review article, Pruitt and co-workers provide guidelines on performing nanoindentation measurements for soft materials and suggest the use of a conospherical tip, displacement-controlled method and a modified trapezoidal function to probe compliant, adhesive materials. This approach was validated by Gallant and co-workers for macro-scale polydimethylsiloxane (PDMS) samples. However, as of today, there are only few reports on the characterization of mechanical properties of microscale 3D printed soft elastomers using nanoindentation, with a lack of clear methodology. Accardo and co-workers studied mechanical properties of 3D printed PDMS microstructures (IP-PDMS, Nanoscribe GmbH & Co. KG) using nanoindentation with a conospherical tip. By varying the printing parameters, a wide range of stiffness varying between 0.35-17.8 MPa was reported, although adhesion effects were not taken into consideration. The lack of standardization for performing nanoindentation on microscopically patterned elastomeric materials increases the risk of variability and potentially reporting erroneous results, especially as measurements become more sensitive to experimental conditions and equipment parameters. Since elastomeric microprinted structures, and in particular PDMS-based inks, are used for cellular biology experiments, obtaining accurate mechanical properties characterization data of such microscaffolds is of essence. Herein, we report a standardized nanoindentation protocol for benchmarking of mechanical properties characterization of 3D printed elastomers on the microscale (Figure ). This protocol is developed following a stepwise optimization of the different testing parameters (indentation tip geometry, displacement profile, peak indentation depth and selecting a suitable model for data analysis and extraction of the mechanical properties). The standardization and benchmarking were performed by thoroughly evaluating the mechanical properties of soft elastomeric microstructures printed by two-photon 3D laser printing (2PLP) using four different PDMS-based elastomer inks, developed for this purpose. This new protocol uses a small-diameter conospherical tip, that allows the high spatial resolution needed for 3D printed microscale objects. In order to record adhesion effects during approach and withdrawal from the sample, modified displacement-controlled displacement profiles including lift-off segments at the start and end of the indent were employed. Moreover, appropriate contact models, such as the nano-Johnson-Kendall-Roberts (nano-JKR) model, have been employed to analyze the nanoindentation data. The mechanical properties obtained using the proposed protocol were compared to a state-of-the-art literature reported nanoindentation protocol using a Berkovich tip and the Oliver-Pharr (OP) model. . The results show significant differences in the mechanical properties reported for 3D printed soft elastomeric materials, and point out the significance of the standardized protocol proposed.