Hello!Thank you for contacting Spa Sciences! The NURI has EMS technology. EMS is electronic muscle stimulation which is what helps to keep the muscles toned and skin-taught. You may feel the EMS more if the face is wet or damp or while using the face masks. EMS is optional. Used on all light modes except purple. You may also press the plus & minus buttons on the device to change the intensity of the unit. You do not need to attach a mask to your NURI device for each use you may use any topical skin care with this device. You may use your favorite serums/moisturizers with the NURI or alone just for the LED light benefits. You may also use NURI over sheet masks! You may use your NURI device as needed and the LED lights as frequently as you would like. We recommend 1-3 minutes per area. Red (anti-aging) Blue (acne) Green (brightness) Purple (repairing damaged skin). We have provided the NURI user manual here:https://cdn.shopify.com/s/files/1/0067/4217/9913/files/NURI_Quick_Start_Guide_REVISED.pdf?v=1639655102. Please make sure to register your device on our website for the warranty (https://spasciences.com/pages/device-registration). We hope this helps.