The answer is atom because it cannot be broken down into small substances
No matter how big or little a material is, its properties remain the same. Size, form, color, and mass are the qualities that distinguish a material from non-substances. All of these qualities, including size, shape, color, and mass, can be seen and measured. Some characteristics are physical, while others are chemical. Physical characteristics include mass, volume, density, and color. Viscosity and solubility are examples of chemical qualities.
The structure of tofacitinib with explicit carbon and hydrogen is the first attached picture.
The number of carbon atoms in tofacitinib are 16.
The molecular formula of tofacitinib is .
The structure of tofacitinib with all the filled hydrogen atoms is the second attached picture.