The increased importance of social media influencers in marketing activities has been evident in recent years. The purpose of the thesis was to understand the cognitive processing of social media micro influencers’ content and the resultant behavioral outcome of follower engagement and purchase intention. Specifically, it has aimed to evaluate if the format of the content had an impact on cognitive processing and ascertains the resultant outcomes of engagement and purchase intention. Elaboration likelihood model (ELM) adapted to social media, was used, and adopted in the study in order to understand and evaluate the purpose as well as the information process of individuals. The research was narrowed down to the micro-influencers in the fashion and beauty industry sharing content, as the industry's high usage of influencer marketing and disseminating persuasive messages on Instagram. The research was conducted by using the Experimental Vignette Methodology (EVM) in a quantitative experiment. By doing so, it enabled the research to examine the participants' response to natural stimuli with quantitative results. A questionnaire together with exposure to three stimuli were used as instrumental in the collection of data. The sample was collected through social media platforms, mainly Instagram and Facebook, and via email to the students of LTU. The collected data was later analyzed, through SPSS, in two levels: impact and hypothesis testing. The impact measurement was analyzed by using repeated measures ANOVA and later the multilinear regression analysis to test the independent variables of content format relation to the dependent variables of engagement (comment and like) and purchase intention (tendency and likelihood). The findings indicated a support to the existing theory of ELM, by confirming the importance of the argument quality in the persuasive message. High lighting in the importance of text content format,in both engagement via commenting and purchase intention, when the information is processed through the more long-lasting central route. The results contributed to current literature in micro influencer and social media influencer marketing by extending the literature in persuasive messaging in relation to the content format. The research provided practical implications with insights into the cognitive processing of content and its implications in consumer engagement and purchase intention to both managers as well as to the content providers, social media influencers. The study presented relative information for content creation, communication and opened possibilities for further research in persuasive messaging in the micro media influencer segment.