Step 1: Understanding the Concept: 
The question asks about the characteristic subject matter of K.C.S. Paniker, a pioneering modern artist from South India and the founder of the Cholamandal Artists' Village. 
Step 2: Detailed Explanation: 
K.C.S. Paniker was a key figure in the Madras Art Movement. In his later and most famous phase, he moved away from figurative painting to develop a unique abstract style. This style, which he called "Metaphysical landscapes" or part of his "Words and Symbols" series, was heavily influenced by indigenous Indian traditions. His canvases incorporated script-like markings, mathematical equations, astrological charts, and traditional symbols. Therefore, his work is best characterized by the use of diagrams and pictograms. He created a visual language that was abstract and modern, yet deeply rooted in Indian esoteric and folk traditions. While his earlier work might have included figures or motifs, his defining contribution to modern art is his symbolic and calligraphic abstraction. 
Step 3: Final Answer: 
The most characteristic feature of K.C.S. Paniker's mature paintings is the use of diagrams and pictograms.
Rearrange the following parts to form a meaningful and grammatically correct sentence: 
P. a healthy diet and regular exercise 
Q. are important habits 
R. that help maintain good physical and mental health 
S. especially in today's busy world