Carotenoid biosynthesis occurs in both chromoplasts and chloroplasts. The DNA in chloroplasts and chromoplasts is identical. The ancestors of plastids diversified into a variety of plastid types, including chromoplasts. Carotenoids are organic pigments found in the chloroplasts and chromoplasts of plants. Using a light microscope chromoplasts can be differentiated and are classified into four main types. The conversion of chloroplasts to chromoplasts in ripening is a classic example. However, the technique has been successfully applied to the chromoplasts of tomatoes. Etioplasts, amyloplasts and chromoplasts are plant-specific and do not occur in algae. The bright colors often produced by chromoplasts is one of many ways to achieve this. Chromoplasts are not widely studied and are rarely the main focus of scientific research. The plastids (chloroplasts or chromoplasts), are undifferentiated, but are present in rudimentary form (proplastids). In one study, it was found that chromoplasts are still present in white flowers.