The nanoscale molecular composition of kerogen is a challenging parameter to characterize given the chemical and structural complexity exhibited by this important biopolymer. However, kerogen composition will strongly impact its reactivity and so is a critical parameter to understand petroleum generation processes during kerogen catagenesis. The recent advent of tip-enhanced analytical methods, such as atomic force microscopy-based infrared spectroscopy (AFM-IR), has allowed for the major compositional features of kerogen to be elucidated at spatial resolutions at or below 50 nm. Here we apply AFM-IR to examine inertinite, an important kerogen maceral type, from an immature Eagle Ford Shale sample. Our data show that the nanoscale molecular composition of the examined inertinite is: (i) less heterogeneous than other organic matter types from the Eagle Ford Shale and (ii) more hydrogen- and oxygen-rich than inertinite from the New Albany Shale at a similar stage of thermal maturity.