This is one of the letters whose descent through the family is easiest to follow. Its Brahmi form is simple, its later forms across the northern and southern branches keep a visible family resemblance, and a reader who knows a modern Indic alphabet can often recognise the ancestor without being told. That is not true everywhere in the script: several letters changed past recognition, and the conjuncts changed more than the simple letters did.
Comparing one letter across the descendants is the ordinary working method of Indian palaeography, and it produces a picture with two main branches. The northern line runs through the Gupta hands into Siddham, which carried Buddhist texts to China and Japan and is still used there for writing mantras, and into the Nagari group that produced Devanagari, and separately into Sharada in the northwest and the scripts of the Himalayan region. The southern line produces Grantha, from which the Tamil and Malayalam alphabets descend, and the Kannada and Telugu pair, and Sinhala.
A third path runs out of the subcontinent altogether. The chancery script of the Pallava dynasty travelled with Indian religion and Indian administration into mainland and island Southeast Asia and stands behind the Khmer, Mon, Burmese, Thai, Lao, Javanese and Balinese writing systems, which is why this letter has descendants in a dozen countries where no Indian language has ever been spoken.