Original: Increasingly many other loops of biology focus on molecules , either directly studying their interactions in their own right such as in cell biology and developmental biology , or indirectly , where the techniques of molecular biology are used to infer historical attributes of populations or species , as in fields in evolutionary biology such as population genetics and phylogenetics .
Simplified: Molecular biology is the study of biology at a molecular level . The field overlaps with other areas of biology and chemistry , particularly cell biology , genetics , biophysics and biochemistry .