Which Tang or Song invention was the most important?

The invention of printing during the Tang and Song dynasties, particularly movable type printing, is often considered one of the most important innovations. It revolutionized the dissemination of knowledge, making books and literature more accessible to a broader audience. This advancement facilitated the spread of ideas, education, and culture, significantly impacting Chinese society and contributing to the eventual rise of literacy and scholarly pursuits. Additionally, it laid the groundwork for future advancements in communication and information sharing worldwide.