In this paper, crystallization of needle-like crystals is investigated using both experimental and numerical approaches. The structure, morphology, habit, and growth behavior of Irbesatan phase A grown from 2-propanol solution are studied. In this case, molecular modeling shows an unusually high anisotropy of the internal crystal structure, leading to the prediction of an acicular habit which is in good agreement with the experimental habit. Irbesartan phase A is an example of crystals for which the properties are governed by internal properties rather than external properties. The influence of the growth conditions is investigated by in situ and ex situ monitoring, namely optical microscopy and AFM. These investigations show that crystals are agglomerated with the same crystallographic orientation as the individual constituent; this was explained by regular over-and intergrowths as in the case of twinning.