The academic book "Sexual Dimorphism in 2D and 4D Digital Lengths and their Ratio (2D:4D)" offers a comprehensive examination of the digital lengths of the index finger (2D) and ring finger (4D), as well as their ratio (2D:4D) and its significance across various scientific disciplines. The study highlights the relationships between these digital lengths and other physical characteristics, particularly concerning the influence of prenatal testosterone and estrogen. The findings are highly relevant for professionals in the fields of anatomy, anthropology, clinical practice, psychiatry, forensics, and surgery. The book provides valuable analytical data that can be used to identify gender, age, and ethnicity. Additionally, it discusses clinical correlations with various conditions such as cardiovascular diseases, hormonal imbalances, and psychosexual disorders. This foundational research aims to identify the dimorphic nature of digital lengths and their correlations with height, weight, and BMI in the Bangladeshi population.