Many established fruit tree variants, for example, have been derived from biotech methods. However, modern biotechnology crops have gone far beyond the centuries-old techniques used by farmers and horticulturists. These days, maize, soya beans, sugar beet, papaya and certain squashes are all widely grown from variants derived by careful modifications made in the laboratory. So-called genetically modified crops are now grown in around 30 countries around the world. Some people are concerned that the results of cross-fertilisation between such species and natural ones will have unintended consequences, so such crops tend to be monitored carefully.