There is no adequate alternative to testing on a living, whole-body system. Living systems like human beings and animals are extremely complex. Studying cell cultures in a petri dish, while sometimes useful, does not provide the opportunity to study interrelated processes occurring in the central nervous system, endocrine system, and immune system. [9] Evaluating a drug for side effects requires a circulatory system to carry the medicine to different organs. [15] Also, conditions such as blindness and high blood pressure cannot be studied in tissue cultures. [9] Computer models can only be reliable if accurate information gleaned from animal research is used to build the models in the first place. [16] Furthermore, even the most powerful supercomputers are unable to accurately simulate the workings of complex organs such as the brain. [12]