After the development of inflorescence primordia in the first season in Vitis, flower and floral organ differentiation take place in the second season. Aim of this study was to describe the differentiation events which occur in the compound buds and flowers during and after budbreak, and to associate these events with the phenological stages in Merlot (Vitis vinifera L.) grape cultivar. In addition, size of the floral organs was determined using microscopy, after careful examination of samples collected as buds and flowers under microscope at every 5 to 10 days. Between March 10 and May 10 in 2016, five interval stages (complete shaping of stamen and pistil primordia following petal primordia formation) were added. According to the results, differentiation of inflorescence and flower primordia occurred after bud swelling in the spring. Approximately 3 weeks after the appearance of inflorescence primordia, stamen and pistil were visible. The development was complete in the following 3 weeks. Flower primordium was sighted on April 1 and increased its size more than 900% in 5-6 weeks. Primordia of reproductive organ was seen when the 2-4 leaves separated from the shoot. By the time of pistil taking its final shape, there were 6-8 full leaves grown from the shoot and inflorescences were easily distinguishable by the naked eye.