Which work marked the beginnings of Baroque art?

There isn't one single work that definitively marks the beginning of Baroque art. It was a gradual evolution that developed over time, influenced by various factors like the Counter-Reformation and the rise of powerful patrons.

However, some works are often cited as early examples and significant precursors to the fully-fledged Baroque style:

* Michelangelo's *Last Judgment* (1536-1541) in the Sistine Chapel: While still Renaissance in essence, this work features dramatic movement, emotional intensity, and a focus on the human form that foreshadowed Baroque themes.

* Caravaggio's *The Calling of Saint Matthew* (1599-1600): This painting, with its dramatic use of light and shadow (chiaroscuro) and realistic depiction of everyday figures, is often seen as a landmark in the development of Baroque style.

* The *Cappella Cornaro* (1608-1615) by Bernini: This chapel, featuring a dramatic sculpted group of figures and theatrical use of light, is a perfect example of early Baroque artistic ideals.

It's important to note that these are just a few examples, and there were many other artists and works that contributed to the development of Baroque art.

Rather than pinpointing a single work, it's more accurate to say that the Baroque style emerged as a culmination of various artistic trends and influences around the late 16th and early 17th centuries.