Soft tissue characterization is an important process for identifying the mechanical properties that govern the behavior of soft tissues. These properties are often utilized in the medical field for a variety of different reasons such as for tissue regeneration, robot-aided surgery, and for diagnosing diseases in their early stages. However, obtaining the mechanical properties of soft tissues is much more challenging than with traditional materials because of their size and fragility. As a result, soft tissues require unique solutions in order to grip them without causing damages and to measure their strain at smaller length scales. There is also a lack of standardization when it comes to characterizing soft tissues and this limitation can make it difficult for researchers to compare results between studies. To address this critical issue, this thesis reviews the most commonly used soft tissue characterization methods in order to find an ideal method for developing a standardized protocol. Based on the review, tensile testing was selected as the most favorable characterization method because of its straightforward procedure. A sub-microscale tensile testing system was then developed for accurately characterizing soft tissues. The novel tensile testing system was built from a previous indenter to apply and measure forces within the sub-microscale range. The system was also constructed to measure the strain of samples in the sub-microscale range by using a high- resolution optical camera setup. Sample holders made from an acrylic material were designed to hold and align the soft tissues samples during the tensile tests. To validate the system the elastic properties of standard rubbers were measured. Results from these trials showed a less than 2.5% error between the measured and reference values. After it was validated, the system was used to measure the mechanical properties of mice lung tissues. Results from these experiments showed that the elastic modulus of the mice lung tissues were between 3-5 kPa, which closely matches what is seen in the literature. In addition, a low coefficient of variation for the elastic modulus values (5.95%), demonstrated the strong repeatability of the system.