Alcides Villaça is a poet and literary critic who was born in Atibaia, São Paulo, in 1946. Since 1973 he has been a professor in Brazilian literature at the University of São Paulo. His research focuses on modern Brazilian poetry with an emphasis on the works of Carlos Drummond de Andrade, Manuel Bandeira, Ferreira Gullar, and João Cabral de Melo Neto. He also studies the work of Machado de Assis, who is regarded as the greatest writer of Brazilian literature. His volumes of poetry include O tempo e outros remorsos (1975), Viagem de trem (1988), and Ondas curtas (2014). As a literary critic, he wrote Passos de Drummond (2006), the result of decades of research on the work of the poet from Minas Gerais, Brazil. He is a regular contributor to newspapers such as Folha de São Paulo and O Estado de São Paulo. The Invisible is the English edition of his first book for young readers. Andrés Sandoval, born in 1973 in Chile, is an illustrator and graphic artist based in São Paulo, Brazil. He graduated in Architecture and Urbanism at the University of São Paulo in 1999, after which he began working in scenography and cinema. Since 2003, he has developed much of his work in books, prints, and murals. He has been illustrating the section Esquinas in the Brazilian magazine Piauí since 2006. He has created prints and patterns for brands such as L'Occitane, Melissa, and Coca-Cola. His illustrations have been published by Companhia das Letras, Cosac Naify, Editora 34, Planeta Tangerina, Pato Lógico, and the New Yorker, among others.