Riddle

I once was young but now I am old. My grand children come and go, but I still remain. My caretakers and those I interact with trust me because I define them well. They have always taken care of me despite the challenges I face, despite the schemers who want to destroy me thinking my body parts are a cure of some of the diseases affecting them. My guardians have always thought of ways of making me better and some time back they equipped me with a new skill and gave me a tool of trade so that those I interact with can still have hope that I am not living them any soon. Who am I? What's my new skill? What's my tool of trade?