Chronic Pain, Opioid Use, and Epidermal Nerve Fiber Density

Inclusion Criteria: Healthy/All: * Informed consent provided by the participant * Able to read and speak in English * Age 18 to 65 years * Likely to participate in all scheduled evaluations and study procedures IF they are a Chronic Non-Cancer Patients who do NOT take opioid medication they must meet all of the above criteria as well as: Diagnosis of non-cancer chronic pain syndrome (persistent pain lasting longer than 3 months) IF they are a Chronic Non-Cancer Patients who DO take opioid medication they must meet all of the above criteria as well as: * Chronic daily opioid use for longer than 3 months duration * Stable doses of opioid medications for at least 30 days prior to study visit Exclusion Criteria: * Pregnancy * Prisoner * Current clinically significant cardiac, or neurologic disease * Significant skin disorders in lower extremities * Circulatory insufficiency * Open wounds in lower extremity that may interfere with healing * Lidocaine allergy * Currently taking anticoagulation (e.g., Coumadin, Plavix, etc) * Current litigation for chronic pain * Active psychotic or suicidal symptoms * Current drug or alcohol abuse * Neuropathy in upper extremities (hands specifically, PI discretion). * Current or recent use of artificial fingernails or nail enhancements (last 6 months) * Other diagnoses that are not considered minor/stable (PI discretion) * Current or previous cancer diagnosis * Current or previous chemotherapy treatment * No chronic pain conditions (healthy) * Opioid use in the last year (healthy \& non-opioid pts)