its quantum fluctuations induced by the vacuum energy of the inflaton potential. However, the curvaton being light does not decay as rapidly as the inflaton, albeit its slow dynamics leads to its late decay. The relative perturbations between the fields give rise to entropy perturbations, which feed the curvature perturbations. Once the curvaton decays, it con- verts all its entropy perturbations into the adiabatic and nearly scale invariant perturations. One advantage of the curvaton scenario is that it is possible to generate significant non- Gaussianity [126, 131, 132], however the present non-Gaussianity bounds are also tied to the residual isocurvature perturbations [133]. The challenges for the curvaton paradigm are the same as that of the inflaton, if the curvaton decays, then it must excite the (MS)SM degrees of freedom [134–136]. There are also alternative mechanisms to understand the temperature anisotropy in the CMB data without invoking inflation , such as in the case of a bouncing cosmology [137–142], we will briefly discuss some of these scenarios. 

The main goal of this review is to address the origin of infation and curvaton, where they explain the large scale structures, and also the microphysical origin of the inflaton and curvaton. This can be achieved provided they belong to a well-motivated sector of particle physics. Our aim is to review such models in details and some of their cosmological consequences. 

The review is organized as follows. In section (Sec.) II, we recapitulate some basic inflationary cosmology, in particular quantum fluctuations during inflation, multi-field per- turbations, curvaton scenario, non-Gaussianity, challenges and requirements for a successful inflation. In Sec. III, we present some background material for particle physics tools re- quired for inflation and curvaton, we particularly focus on MSSM, renormalization group equations, moduli space of flat directions within MSSM, properties of flat directions and their cosmological consequences, SUGRA and their role in building inflationary models, and a brief discussion on cosmic strings and grand unified theories (GUT). In Sec. IV, we dis- cuss models of inflation, particularly highlighting the connections with particle theory, we discuss non-SUSY models of inflation, SM Higgs inflation and implications for collider and non-collider experiments, SUSY F -and D -term inflation models, and embedding inflation within SUSY GUTs. In Sec. V, we discuss various attempts to gauge the inflaton with the SM charges, we discuss MSSM inflation models where we recognize the inflaton candi- dates. We also consider thermal production of dark matter in conjunction with inflationary parameter space. In Sec. VI, we discuss inflaton decay, reheating and thermalization. We 

