According to the Greek Mythology, a water nymph, Cyltia, was so madly in love with the God of Sun, Apollo, that she never stopped staring up at the sun continuously, but he did not return the love. Taking pity on her, other Gods turned her into a sunflower that could always follow the path of the sun. Therefore, the sunflower has been following the sun ever since.
"I am working with the enthusiasm of a man from Marseilles eating bouillabaisse, which shouldn't come as a surprise to you because I am busy painting huge sunflowers." ― Vincent van Gogh