[23, Piazza della Santissima Annunziata, Florence] The Renaissance lasted roughly two centuries. The High Renaissance or early 1500s is famous for Leonardo, Michelangelo, and Raphael — who we'll get to later. But the first half of the Renaissance, the 1400s, is often overlooked. During this period, there was a steady evolution in art from medieval two-dimensional to more life-like 3-D.

[24, Christ Triumphant altarpiece, c. 1200, unknown Tuscan artist, Uffizi Gallery, Florence] Back in the Middle Ages, altarpieces were far from realistic. Panels, like painted pages, told Bible stories…but with little sense of depth. To show Jesus' head leaning out…it actually does.

[25, Rucellai Madonna, 1285, Duccio, Uffizi Gallery, Florence] Here, angels are stacked on top of each other with no concern for realistic depth. The throne is crudely drawn. It's as if Mary and baby Jesus exist somewhere in a golden never-land. Mary, like a flat cardboard-cutout, seems to float weightlessly.

[26, Virgin and Child Enthroned, c. 1300, Cimabue, Uffizi Gallery, Florence] A decade later, this work takes a few baby steps forward. The throne, while still clunky, shows an attempt to create the illusion of depth. Mary's foot actually sticks out over the edge. But the angels, while now portrayed one behind the other, are still stacked…like heavenly bookends.

[27, Giotto, 1267–1337; Ognissanti Madonna, 1306, Uffizi Gallery, Florence] The great leap forward was made by the pioneering late-medieval artist Giotto. Still a century before the Renaissance, Giotto creates a spacious three-dimensional "stage," and then fills it. There's a realistic canopied throne surrounded by real bodies: angels in front, prophets behind, clearly defining its depth. Mary herself is monumental…you know there's a body under her robe.

[28, Masaccio, 1401–1428; The Tribute Money, 1427, Brancacci Chapel, Florence] Building on Giotto's work, the ground-breaking artist Masaccio gave his figures believability: they had mass, shadows indicated a light source, they came with a range of emotions. And Masaccio portrayed the illusion of depth like never before. He masterfully captured the three-dimensional world on a two-dimensional surface.

[29, Holy Trinity, 1427, Masaccio, Santa Maria Novella, Florence] Masaccio painted this believable scene on a flat church wall. He used math to create linear perspective. Parallel lines would converge at what's called the "vanishing point." With this revolutionary technique, it's as if Masaccio blew a hole in that wall, creating a chapel, and letting worshippers feel like they're standing in the presence of the Holy Trinity…portrayed here before our very eyes: God the father, the son, and a dove representing the Holy Spirit.

[30, Fra Angelico, 1395–1455; frescoes in each monk's cell in San Marco Monastery, Florence] Masaccio influenced the early Renaissance artist Fra Angelico — a humble monk as well as a great painter. Using the fresco technique — where the plaster is put on the wall, then painted while still wet — he decorated the walls of his own monastery, giving each cell a meditation-enhancing scene.

[31] For Fra Angelico, painting was a form of prayer, and it's said he couldn't paint a crucifix without shedding tears. He fused medieval spirituality with groundbreaking Renaissance techniques to achieve a new level of realism…drama…and emotional impact.

[32, Deposition of Christ, 1434, Fra Angelico, San Marco Museum, Florence] His painting of the Deposition (Christ taken down from the cross) was no longer just a symbol of the crucifixion, but featured a real man mourned by both haloed saints and contemporary Florentines, amid a very real setting — one of the first great landscapes ever painted. And this holy scene is not in faraway Jerusalem but on a lawn in Tuscany…among real trees and everyday people…bringing the Bible lesson closer to home.

[33, Annunciation, c. 1450, Fra Angelico, San Marco Museum, Florence] This Fra Angelico scene of the Annunciation — the angel telling Mary she'll give birth to the Messiah — greeted monks at the top of the stairs as they headed to their cells. It's set in an everyday garden, beneath a shady arcade — with receding columns creating a sense of depth…bringing this heavenly scene down to earth.

[34, Madonna and Child, 1465, Filippo Lippi] Increasingly, Renaissance artists were enlivening their subjects. Here Mary and her child are portrayed with a new playfulness…complete with a couple of cheeky angel boys. Even without the gold plate halo, we know she's holy — she radiates sweetness and light from her divine face.