Below are the important topics for AIIMS

Biology:  Systematics, Genetics, Cells, Ecology and Human Health & Diseases are especially important.

Chemistry: General Organic Chemistry (EXTREMELY IMPORTANT), Hydrocarbons, Equilibria, Bonding etc. Also, be very thorough with reactions of p-block elements.

Physics: Modern Physics, Waves, Heat and Thermodynamics, Ray Optics etc.

All the Best!!