Working in Figurative Realism with Impressionist influences, Diego Cuéllar applies the "alla prima" method, painting directly onto canvas or wood without preliminary sketches. Drawing on a background in management and shaped by his family's artistic heritage, he turned to painting later in life. His work centers on light and contrast, aiming to reveal the essence of his subjects while focusing on themes of neurodiversity and the lived experience of Fragile X Syndrome—a condition affecting both his children. Cuéllar is also the author of "Beneath the Same Sky," a book examining resilience and human fragility beyond conventional measures of success.