Finding drugs for diseases has been an age-old practice that humanity has been involved in. But with time, the pattern of drug molecules has changed. Medical research is slowly shifting towards relying more on large molecules, even as drugs from earlier days were more focused on the small molecules. The shifting trend, however, hasn’t been able to replace the small molecules completely as potential drug molecules. Veteran scientist Satyajit Rath talks about the differences, usefulness and the pros and cons of small and big molecules as constituents of drugs.