Microscale BHO refers to a small scale process of preparing butane honey oil, a type of marijuana extract made by passing liquid butane through a tube containing finely ground marijuana. Microscale BHO uses the same basic method as larger scale extraction, but only prepares enough for a few people to get high from at a time. Plastic bic pen tubes are common devices for the extraction, holding ~1g of marijuana at a time. The small amount of butane used makes it safe to perform inside though care must still be taken to avoid open flames and sparks. Other advantages are that it takes only a few minutes to prepare and only requires a small amount of weed at a time.
The two main ways of consuming the product are to extract directly onto some other marijuana to make super potent marijuana or to extract into a foil dish or lightbulb vaporizer from which the BHO can be vaporized. When the latter method is used, little odor is produced and higher efficiency is attained since the product vaporizes rapidly enough that little THC is broken down.
Adam and Rob wanted some BHO, but couldn't make a lot since they were in a dorm room so they did a microscale BHO extraction and got really high.