Cessation Intervention: Participants in the Cessation Intervention group will be divided into two groups (have intention to quit vs. not have intention to quit) based on the participants' stage of change (Transtheoretical Model) \[1\] at baseline assessment to receive different message libraries during the 12 week intervention. Participants who have intention to quit (at the action or preparation stage of change) will set the quit date at time of enrollment to the study. The two weeks before the quit date, participants will receive 2 messages per day with content focusing on health benefits of quitting, monetary costs of smoking, encouragement and some tips/strategies to prepare for the quit date. Two days around the quit date, participants will receive 3-4 messages per day, and the first five weeks participants will receive 2 messages per day. The content of messages in the first five weeks after the quit date is diverse, providing participants a lot of tips/strategies (including mindfulness practice) to deal with cravings/withdrawal symptoms, benefits of quitting, interactive messages asking the participants' mood and craving levels, motivating messages and encouraging to get supports from family/friends and other smoking cessation resources (i.e., quit line, website). During this period, participants will periodically be asked about maintain smoke-free, and based on the particpants' answer, further messages will provide encouragement to get back on track or stay focus to avoid relapse. From week 6 to week 12, participants will just receive one message per day, with content covers benefits of quitting smoking, motivating messages, tips to avoid cravings/relapse, and interactive messages asking about the participants' smoke free status. Participants who do not have intention to quit will receive messages from another library, with the frequency of one message per day throughout 12 weeks of the intervention. This message library will provide participants knowledge of negative effects of smoking with specific evidences, benefits of quitting, encouraging messages as well as messages to increase the participants self-efficacy in quitting smoking. From week 2 to week 7, participants in this group will receive an interactive message on every 7-day period, asking if the participants want to set a quit date in the next week. If participants answer yes to the question, the participants will be switch to the message library for those who have intention to quit as mentioned above.

Education Intervention Group and Control Group: Participants in the Education Intervention and Control groups will also receive one single message per day for the entire 12-week intervention period. Education Intervention messages will specifically focus on the health risks of smoking and secondhand smoking (i.e., education about health risks, without providing specific strategies for quitting). These messages will be taken from the text message library developed by NCI, and will be directly translated into Chinese and Vietnamese without cultural adaptions. Control messages will provide general health education (not including smoking), including promoting fruit and vegetable intake and low sodium intake; encouraging physical activity; and avoiding drug use/excess alcohol use. These messages will be translated from previous studies that use mHealth approaches to promote healthy lifestyles.