Not much is known about Masaccio other than the fact he must have admired and studied deeply the work of Giotto in the Church of Santa Croce in Florence. At the age of 21 he became a member of the painter's guild and began his life's work in painting a series of frescos in the Brancacci Chapel sometime after 1425.
"In sculpture Donatello had already given body to the new ideals when Masaccio began his brief career, and in the education, the awakening, of the younger artist the example of the elder must have been of incalculable force. But a type gains vastly in significance by being presented in some action along with other individuals of the same type; and here Donatello was apt, rather than to draw his meed of profit, to incur loss by descending to the obvious - witness his bas reliefs at Siena, Florence, and Padua. Masaccio was untouched by this taint. Types, in themselves of the manliest, he presents with a sense for the materially significant which makes us realize to the utmost their power and dignity; and the spiritual significance thus gained he uses to give the highest import to the event he is portraying; this import, in turn, gives a higher value to the types, and thus, whether we devote our attention to his types or to his action, Masaccio, keeps us on a high plane of reality and significance. In later painting we shall easily find greater science, greater craft, and greater perfection of detail, but greater reality, greater significance, I venture to say, never. Dust bitten and ruined though his Brancacci Chapel frescoes now are, I never see them without the strongest stimulation of my tactile consciousness. I feel that I could touch every figure, that it would yield a definite resistance to my touch, that I should have to expend thus much effort to displace it, that I could walk around it. In short, I scarcely could realize it more, and in real life I should scarcely realize it so well, the attention of each of us being too apt to concentrate itself upon some dynamic quality, before we have at all begun to realize the full material significance of the person before us. Then what strength to his young men, and what gravity and power to his old! How quickly a race like this would possess itself of the earth, and brook no rivals but the forces of nature! Whatever they do - simply because it is they - is impressive and important, and every movement, every gesture, is world changing. Compared with his figures, those in the same chapel by his precursor, Masolino, are childish, and those by his follower, Filippino, unconvincing and without significance, because without tactile values. Even Michelangelo, where he comes in rivalry, has, for both reality and significance, to take a second place. Compare his 'Expulsion from Paradise' (in the Sixtine Chapel) with the one here by Masaccio. Michelangelo's figures are more correct, but far less tangible and less powerful; and while he represents nothing but a man warding off a blow dealt by a sword, and a woman cringing with ignoble fear, Masaccio's Adam and Eve stride away from Eden heart broken with shame and grief, hearing, perhaps, but not seeing, the angel hovering high overhead who directs their exiled footsteps.
Masaccio, then, like Giotto a century earlier - himself the Giotto of an artistically more propitious world - was, as an artist, a great master of the significant, and, as a painter, endowed to the highest degree with a sense of tactile values, and with a skill in rendering them. In a career of but few years he gave to Florentine painting the direction it pursued to the end. In many ways he reminds us of the young Bellini. Who knows? Had he but lived as long, he might have laid the foundation for a painting not less delightful and far more profound than that of Venice. As it was, his frescoes at once became, and for as long as there were real artists among them remained, the training school of Florentine painters."
[From Bernard Berenson, "Italian Painters of the Renaissance"
Berenson published his first book, Venetian Painters of the Renaissance, in 1894, and followed quickly with other books on the painters of Florence and central and northern Italy, Florentine Painters of the Renaissance, 1896, and Central Italian Painters of the Renaissance, 1897. Along with a book he wrote in 1907, North Italian Painters of the Renaissance, all of his early works were collected into one volume in 1930, The Italian Painters of the Renaissance. That book served as the definitive authority on Italian Renaissance painting throughout the 20th century.]
 Vasari's changes. The church initially had been divided into two parts - the higher part was divided by a wall and reserved for the friars while the lower part was open to the faithful that entered by the eastern side door. The wall was demolished by Vasari in the 16th century but you can clearly see where the division used to be as Giotto's Crucifix hangs right above. This also explains why the pulpit is so far down the church in the lower part.
The side door was also closed off by Vasari and was just reopened in 2000 on occasion of the Jubilee celebrations which permits once again to correctly observe Masaccio's Trinity as it was intended.
 McCarthy, Mary (August 22, 1959). "A City of Stone". The New Yorker (New York): 48.