Do not waste Your money on the Carson microscope attachment (especially the one for smart phones). I bought one a year and a half ago and it was a total waste! I did find a clip on lens for my iPhone 4 (and will work on others) that works very well. It is an Apexel 20X Macro I got on Amazon for around $10. It has a clear, undistorted image, comes with a cleaning cloth and a foam case, well worth the price. My avatar photo was taken using the lens on my iPhone 4.
Good luck with Your growing.