"The Painting That Started The Renaissance"

Masaccio
Holy Trinity

Tomasso Masaccio' Holy Trinity is cited by some as being the first painting of the Renaissance. It is a fresco in Santa Maria Novella in Florence.

From Wikipedia:

The fresco had a transforming effect on generations of Florentine painters and visiting artists.

Masaccio
Holy Trinity detail

Masaccio
Holy Trintiy detail: Memento mori skeleton