 First, we do not understand three crucial components of the SM that require new physics. We do not have a full account of the nature, or underlying dynamics, of dark matter (Bertone et al. 2005), dark energy (Peebles &amp; Ratra 2003), or the inflaton field (Lyth &amp; Riotto 1999; Martin et al. 2014). These are well-recognized problems that have inspired active theoretical and observational work, although as we note below in  §2.4  they will be challenging to resolve due to inaccessibility of physics at the appropriate scale.