In Thee Rejoiceth also known as Epi Si Harri is a tempera and gold leaf painting by Theodore Poulakis. The central figure of the piece is the Virgin Mary. The painting is a tribute to her. Poulakis was from Chania Crete. He was active on the Ionian islands and in Venice during the second half of the 17th century. He was a member of the Cretan School and the father of the Heptanese School. According to the Institute of Neohellenic Research, 130 paintings are attributed to Poulakis.

Theodore Poulakis was a Greek Renaissance painter and teacher. He is considered the father of the Heptanese School and one of the most prolific painters of Venetian Crete. Poulakis was a member of the Cretan School, his contemporary was Emmanuel Tzanes. Emmanuel Tzanes and Poulakis were active painters of the Cretan School until Candia, went to war with the Ottomans around 1649. Candia finally fell after twenty years of siege in 1669. Poulakis settled on the island of Corfu. Stephanos Tzangarolas was another famous painter in Corfu around the same period. Poulakis's works are likened to Andreas Pavias and Georgios Klontzas. Poulakis works exhibit qualities of the Venetian school. Over 130 of his paintings have survived and can be found all over the world.