Executed at the dawn of the new millennium, just four years before Agnes Martin tragically passed away, Untitled is a breathtakingly assured example of the artist’s mesmerising, striated facture. Soft washes of hazy powder blue, chalky yellows and pinkish bands trace horizontally across the work’s surface, inviting the viewer to wallow and immerse themselves in the sheer joy, tranquillity, peace and happiness that this sublime work evokes. These hypnotic waves of diaphanous colour render Untitled truly exceptional in the artist’s later practice. Since Martin had moved to New Mexico in 1968, her works had been populated by greys, whites and blacks, and it was only when her deteriorating health caused her to move to an assisted living facility in Taos in 1993, that she began to experiment with colour once more. Here she reduced the size of her paintings from her monumental 72 by 72 inch canvases, to the more intimately scaled 60 by 60 inch size of the present work, so that she could handle them more easily. Created at the very apex of her long and illustrious career, just a year after she received the Distinguished Artist Award for Lifetime Achievement from the College Art Association as well as the National Medal of Arts from the Office of President Bill Clinton, Untitled is the perfect culmination of Martin’s prodigious output. Reaffirming Martin's status as one of the most dynamic and prestigious artist's of our times, a major retrospective of the artist's work opened at Tate Modern, London this summer. To craft the shimmering surfaces of Untitled, Martin would first draw clear lines in graphite across the uneven surface of the gesso to apportion the colour fields into different bands. The gesso ground plays a crucial role in Martin’s incandescent facture imbuing the paint with a unique spatial depth and luminosity. When her thinned acrylic was applied to the chalky white primer, the colours both absorbed and reflected light, adding a particular radiance that appears to disintegrate the painting into atmospheric light. The innovative reddy-pink hue in the present work, for example, is created by mixing a blend of pink with a tinge of warmer orange that when placed on the white ground seems to emit light from within. Other irregularities are visible in the particular nature of the paint application, which has been applied by hand using masking tape to give the straight lines that we see in Untitled. It is precisely these touches of imperfection that gives the present work its singular vitality and strength.\nMartin’s practice can be divided into two clear phases: first the paintings she created up until 1967, when she left New York and embarked upon a five year hiatus from painting; second the work that she began to create in New Mexico from 1972 until her death in Taos in 2004. The first period is primarily characterised by her early experiments into abstraction and is heavily influenced by early Abstract Expressionism, Surrealism and geometric compositions. These forays into abstraction culminated in what we might call the artist’s ‘classical’ phase – her now iconic, meticulously drawn pencil grids on large white canvases. This early period overlapped with a tempestuous few years in the artist’s life, which were blighted by a desperate need to earn money, and the artist having to deal with episodes of mental illness. The second period is much less developmental than the first, and is typified by Martin refining the nuances of her already perfected praxis. The new paintings, although rooted in her innate sensibilities, represented a series of shifts in the structure of the canvas and the use of colour. Martin maintained the logic of the grid, but now revelled in a more painterly approach. It is at the very zenith of this period that Untitled is situated. With only a few exceptions, works from these thirty years were created in series, which contained between eight and twenty interrelated paintings.\nThe influence of the thirty years that Martin spent in the wide, open planes of Taos, New Mexico, is readily felt in both the broad open bands of Untitled and the intellectual framework through which the work was conceived. The artist first visited New Mexico as student and teacher at the University of Albuquerque and Taos in the period between 1946-49. Here, she was immediately struck by the burgeoning community of artists and writers who had come to call this small pocket of New Mexico home. Nestled between majestic mountain ranges and home to an ancient Native American population, this small town has attracted a steady stream of creative individuals who have flocked there since the late Nineteenth Century to get away from modern life and to embrace nature to its full. Artists such as Edward Hopper and writer D.H. Lawrence visited, whilst Martin’s idol Georgia O’Keefe had famously moved to New Mexico in 1940. In the years that followed World War II a new group of artists including Richard Diebenkorn, Ad Reinhardt and Mark Rothko visited the locale. The influence that these artists had on Untitled is immeasurable: the transparent, ghostly geometric shapes of works such as Reinhardt’s Untitled 107, are mirrored in the present work’s spectral stripes that appear to hover in front of its incandescent ground, whilst the poetry of the repeating diaphanous veils of colour that flow across the surface of the work are redolent of Rothko’s iconic colour-field paintings. Describing her mental shift when she moved to New Mexico, Martin eloquently described it as though from “joy to happiness” (Agnes Martin quoted in: Exhibition Catalogue, London, Tate Modern, (and travelling), Agnes Martin, 2015, p. 29).\nIn Untitled the tightly packed pencil markings of the 1960s have given way to broader bands of lightly tinted colour, in part inspired by the limitless vistas of both sky and sand that surrounded her in New Mexico. The lines are still barely visible, as if mirages emerging or disappearing in the desert sun. The power of symmetry has remained although the geometric components could now be singular, either vertical or horizontal, and her compositions are more elastic as thin bands of blue alternate with thick ones of pale red and yellow in the present painting. The delicate ebb and flow of the softly gradated tones in Untitled are a subtly layered visual pleasure, constrained within the pencil demarcations while it also visually vibrates from the painting's surface. Indeed, the painting’s innate rhythms are also born of these harmonious, delicate changes in colour. Colour dematerialises and light seems to emanate from the canvas with an extraordinary radiance, as though it were emitting rays of light into the space around it. The natural landscape certainly permeated many of her paintings and she famously compared the experience of looking at her work to “watching clouds and never seeing any the same, or viewing waves of the sea, continuously breaking on the shore always the same but always different” (Ibid.). In Untitled one can imagine the artist looking out over the Taos landscape, stirred by the resplendent atmosphere and austere tranquillity of the desert.\nIt is often remarked that Martin’s late works created in her assisted living home, like Untitled, are amongst her most beautiful and joyous. As is so masterfully expounded in the present work, this happiness operates as though another powerful energy emanating from within the painting, which threatens to subsume and take hold the viewer in all its delight. As the artist lyrically explains “The value of art is in the observer. When you find out what you like, you’re really finding out about yourself. Beethoven’s music is joyous. If you like his music, you know that you like to be joyful. People who look at my painting say that it makes them happy, like the feeling when you wake up in the morning. And happiness is the goal, isn’t it?” (Ibid., p. 31). Remarkable not only for its exuberant emanations, its late use of colour and its intimate scale, Untitled is one of Martin’s very best and last ever paintings.