As the use of nanotechnology continues to rise, the release of engineered nanomaterials into the environment becomes inevitable. A need exists to understand the implications of engineered nanomaterials and to develop sustainable alternatives as adverse impacts are uncovered. In order to reduce any negative impacts of nanomaterials and exploit any beneficial impacts, the field of environmental nanotechnology must aim to understand the behavior of nanomaterials in complex environments through the use of in situ analytical methods and utilize model systems (both in terms of nanomaterials and organisms) to determine the chemical factors that drive nanoparticle behavior. The work presented here focuses on the cellular membrane, which is hypothesized to be the first point of contact between a nanomaterial and an organism. The characterization of different models cellular membranes and the characterization of nanoparticle interactions at these model membranes are presented. First, we investigated the impact of natural organic matter (NOM), which is found ubiquitously in the environment, on the interactions between polymer wrapped diamond nanoparticles (DNPs) and lipopolysaccharide-containing supported lipid bilayers, a model for Gram-negative bacteria cell membranes. To demonstrate the relevance of our model system we extended our study to include experiments using a Gram-negative bacterium, Shewanella oneidensis MR-1.We found that NOM impacted the hydrodynamic and electrokinetic properties of DNPs in a concentration dependent manner, which altered subsequent interactions with both model and actual biological membranes. Our results demonstrate that the effects of NOM coronas on nanoparticle properties and interactions with biological surfaces can depend on the relative amounts of NOM and nanoparticles. We then examined the impact of polymer wrapped quantum dots (QDs) on supported lipid bilayers containing important biomolecules found in the outer membrane of eukaryotic cells (cholesterol and sphingomyelin). We used in situ analytical methods to study these interactions in real time and found that the QDs caused structural changes to the bilayers studied. Quartz crystal microbalance with dissipation monitoring coupled with nanoplasmonic sensing revealed favorable interaction between the QDs and the bilayers. Increases in dissipation and apparent mass gains upon rinse suggested structural rearrangement was occurring. Time-lapsed atomic force microscopy confirmed this hypothesis and revealed the disappearance of phase-segregated domains upon interaction with the QDs. Our results demonstrate the importance of using complementary in situ analytical methods to understand the complex interactions that occur at the cellular membrane. We next demonstrate the powerful capabilities of atomic force microscopy for imaging and characterizing biological membranes. We investigate the impact of the substrate in the formation and characteristics of phase-segregated domains in supported lipid bilayers. We considered commonly used substrates in different analytical techniques (e.g., mica, silica, and glass). We discussed the importance of considering the substrate in drawing conclusions across different techniques. We also demonstrated the spatial and temporal correlation of atomic force and fluorescence microscopy. Finally, we extended our work using atomic force microscopy and developed a protocol to image and characterize the mechanical properties of fixed and live rainbow trout (Oncorhynchus mykiss) gill epithelial cells. We discussed various experimental variables such as instrumental parameters, type of AFM probe used, and the confluency of the cells on the substrate. We found that the ideal imaging conditions included using an AFM probe with a low spring constant and relatively dull tip, working with cells grown to ~75% confluency, and scanning at low speeds, high amplitudes, and minimal forces. We showed that fixed trout gill cells had an increased height and modulus value as compared to live cells. This work demonstrated the first example of AFM imaging and mechanical mapping on either fixed or live trout gill cells and set a protocol to examine the impacts of different stressors, such as nanomaterials, on trout gill cells.